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	$91.34	13.591%	$103.754	$103.75	$103.75	$103.80
Purchase #2	$173.49	10.459%	$191.6353	$191.64	$191.65	$191.60
Purchase #3	$238.67	4.442%	$249.2717	$249.27	$249.25	$249.30
Purchase #4	$190.60	12.448%	$214.3259	$214.33	$214.35	$214.30
Purchase #5	$45.54	5.825%	$48.1927	$48.19	$48.20	$48.20
Purchase #6	$115.81	11.161%	$128.7356	$128.74	$128.75	$128.70
Purchase #7	$196.25	13.445%	$222.6358	$222.64	$222.65	$222.60
7 purchase totals =	$1,051.70		$1,158.5510	$1,158.56	$1,158.60	$1,158.50