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	$154.88	6.177%	$164.4469	$164.45	$164.45	$164.40
Purchase #2	$6.32	13.134%	$7.1501	$7.15	$7.15	$7.20
Purchase #3	$166.97	10.593%	$184.6571	$184.66	$184.65	$184.70
Purchase #4	$71.73	10.799%	$79.4761	$79.48	$79.50	$79.50
Purchase #5	$219.98	10.656%	$243.4211	$243.42	$243.40	$243.40
Purchase #6	$88.50	13.556%	$100.4971	$100.50	$100.50	$100.50
Purchase #7	$213.37	4.811%	$223.6352	$223.64	$223.65	$223.60
7 purchase totals =	$921.75		$1,003.2836	$1,003.30	$1,003.30	$1,003.30