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	$38.55	13.181%	$43.6313	$43.63	$43.65	$43.60
Purchase #2	$247.97	7.718%	$267.1083	$267.11	$267.10	$267.10
Purchase #3	$175.78	7.172%	$188.3869	$188.39	$188.40	$188.40
Purchase #4	$92.71	8.113%	$100.2316	$100.23	$100.25	$100.20
Purchase #5	$150.78	5.825%	$159.5629	$159.56	$159.55	$159.60
Purchase #6	$90.28	6.122%	$95.8069	$95.81	$95.80	$95.80
Purchase #7	$64.93	7.104%	$69.5426	$69.54	$69.55	$69.50
7 purchase totals =	$861.00		$924.2705	$924.27	$924.30	$924.20