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	$147.81	11.334%	$164.5628	$164.56	$164.55	$164.60
Purchase #2	$126.33	8.702%	$137.3232	$137.32	$137.30	$137.30
Purchase #3	$219.29	4.549%	$229.2655	$229.27	$229.25	$229.30
Purchase #4	$167.48	4.439%	$174.9144	$174.91	$174.90	$174.90
Purchase #5	$101.64	9.320%	$111.1128	$111.11	$111.10	$111.10
Purchase #6	$188.26	8.380%	$204.0362	$204.04	$204.05	$204.00
Purchase #7	$120.52	8.654%	$130.9498	$130.95	$130.95	$130.90
7 purchase totals =	$1,071.33		$1,152.1647	$1,152.16	$1,152.10	$1,152.10