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	$202.91	10.319%	$223.8483	$223.85	$223.85	$223.80
Purchase #2	$169.25	7.751%	$182.3686	$182.37	$182.35	$182.40
Purchase #3	$77.27	10.547%	$85.4197	$85.42	$85.40	$85.40
Purchase #4	$154.42	6.397%	$164.2982	$164.30	$164.30	$164.30
Purchase #5	$164.67	9.518%	$180.3433	$180.34	$180.35	$180.30
Purchase #6	$153.29	6.272%	$162.9043	$162.90	$162.90	$162.90
Purchase #7	$123.67	5.869%	$130.9282	$130.93	$130.95	$130.90
7 purchase totals =	$1,045.48		$1,130.1106	$1,130.11	$1,130.10	$1,130.00