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	$108.33	3.109%	$111.698	$111.70	$111.70	$111.70
Purchase #2	$203.84	8.569%	$221.307	$221.31	$221.30	$221.30
Purchase #3	$173.47	6.470%	$184.6935	$184.69	$184.70	$184.70
Purchase #4	$146.25	3.124%	$150.8189	$150.82	$150.80	$150.80
Purchase #5	$124.80	5.818%	$132.0609	$132.06	$132.05	$132.10
Purchase #6	$98.34	11.120%	$109.2754	$109.28	$109.30	$109.30
Purchase #7	$159.48	7.826%	$171.9609	$171.96	$171.95	$172.00
7 purchase totals =	$1,014.51		$1,081.8146	$1,081.82	$1,081.80	$1,081.90