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	$96.90	5.136%	$101.8768	$101.88	$101.90	$101.90
Purchase #2	$35.32	4.112%	$36.7724	$36.77	$36.75	$36.80
Purchase #3	$228.37	9.200%	$249.38	$249.38	$249.40	$249.40
Purchase #4	$187.83	6.780%	$200.5649	$200.56	$200.55	$200.60
Purchase #5	$150.32	5.751%	$158.9649	$158.96	$158.95	$159.00
Purchase #6	$216.37	3.324%	$223.5621	$223.56	$223.55	$223.60
Purchase #7	$61.49	5.792%	$65.0515	$65.05	$65.05	$65.10
7 purchase totals =	$976.60		$1,036.1726	$1,036.16	$1,036.15	$1,036.40