Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$98.56	8.473%	$106.911	$106.91	$106.90	$106.90
Purchase #2	$211.72	6.310%	$225.0795	$225.08	$225.10	$225.10
Purchase #3	$129.28	7.530%	$139.0148	$139.01	$139.00	$139.00
Purchase #4	$138.73	5.703%	$146.6418	$146.64	$146.65	$146.60
Purchase #5	$122.48	13.778%	$139.3553	$139.36	$139.35	$139.40
Purchase #6	$153.78	5.454%	$162.1672	$162.17	$162.15	$162.20
Purchase #7	$146.78	11.841%	$164.1602	$164.16	$164.15	$164.20
7 purchase totals =	$1,001.33		$1,083.3298	$1,083.33	$1,083.30	$1,083.40