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	$126.68	3.504%	$131.1189	$131.12	$131.10	$131.10
Purchase #2	$233.93	8.215%	$253.1473	$253.15	$253.15	$253.10
Purchase #3	$85.77	8.341%	$92.9241	$92.92	$92.90	$92.90
Purchase #4	$120.37	7.312%	$129.1715	$129.17	$129.15	$129.20
Purchase #5	$185.68	12.730%	$209.3171	$209.32	$209.30	$209.30
Purchase #6	$115.77	6.262%	$123.0195	$123.02	$123.00	$123.00
Purchase #7	$212.52	10.802%	$235.4764	$235.48	$235.50	$235.50
7 purchase totals =	$1,080.72		$1,174.1748	$1,174.18	$1,174.10	$1,174.10