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	$60.35	6.356%	$64.1858	$64.19	$64.20	$64.20
Purchase #2	$148.67	7.515%	$159.8426	$159.84	$159.85	$159.80
Purchase #3	$127.26	3.459%	$131.6619	$131.66	$131.65	$131.70
Purchase #4	$174.36	4.190%	$181.6657	$181.67	$181.65	$181.70
Purchase #5	$38.98	9.606%	$42.7244	$42.72	$42.70	$42.70
Purchase #6	$244.96	3.599%	$253.7761	$253.78	$253.80	$253.80
Purchase #7	$168.33	8.385%	$182.4445	$182.44	$182.45	$182.40
7 purchase totals =	$962.91		$1,016.3010	$1,016.30	$1,016.30	$1,016.30