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	$216.69	6.675%	$231.1541	$231.15	$231.15	$231.20
Purchase #2	$125.89	4.793%	$131.9239	$131.92	$131.90	$131.90
Purchase #3	$124.58	9.822%	$136.8162	$136.82	$136.80	$136.80
Purchase #4	$80.52	3.787%	$83.5693	$83.57	$83.55	$83.60
Purchase #5	$96.61	5.229%	$101.6617	$101.66	$101.65	$101.70
Purchase #6	$182.67	11.686%	$204.0168	$204.02	$204.00	$204.00
Purchase #7	$123.62	4.603%	$129.3102	$129.31	$129.30	$129.30
7 purchase totals =	$950.58		$1,018.4522	$1,018.45	$1,018.35	$1,018.50