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	$240.62	12.663%	$271.0897	$271.09	$271.10	$271.10
Purchase #2	$156.46	3.858%	$162.4962	$162.50	$162.50	$162.50
Purchase #3	$5.44	3.219%	$5.6151	$5.62	$5.60	$5.60
Purchase #4	$64.28	4.332%	$67.0646	$67.06	$67.05	$67.10
Purchase #5	$82.64	9.649%	$90.6139	$90.61	$90.60	$90.60
Purchase #6	$39.87	3.250%	$41.1658	$41.17	$41.15	$41.20
Purchase #7	$247.89	3.521%	$256.6182	$256.62	$256.60	$256.60
7 purchase totals =	$837.20		$894.6635	$894.67	$894.60	$894.70