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	$197.84	4.834%	$207.4036	$207.40	$207.40	$207.40
Purchase #2	$197.30	13.115%	$223.1759	$223.18	$223.20	$223.20
Purchase #3	$89.72	3.800%	$93.1294	$93.13	$93.15	$93.10
Purchase #4	$75.67	4.252%	$78.8875	$78.89	$78.90	$78.90
Purchase #5	$33.93	11.815%	$37.9388	$37.94	$37.95	$37.90
Purchase #6	$203.79	9.612%	$223.3783	$223.38	$223.40	$223.40
Purchase #7	$126.60	11.217%	$140.8007	$140.80	$140.80	$140.80
7 purchase totals =	$924.85		$1,004.7142	$1,004.72	$1,004.80	$1,004.70