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	$103.88	7.731%	$111.911	$111.91	$111.90	$111.90
Purchase #2	$191.40	3.612%	$198.3134	$198.31	$198.30	$198.30
Purchase #3	$63.89	6.735%	$68.193	$68.19	$68.20	$68.20
Purchase #4	$68.63	4.336%	$71.6058	$71.61	$71.60	$71.60
Purchase #5	$149.39	7.535%	$160.6465	$160.65	$160.65	$160.60
Purchase #6	$224.63	8.222%	$243.0991	$243.10	$243.10	$243.10
Purchase #7	$114.91	7.813%	$123.8879	$123.89	$123.90	$123.90
7 purchase totals =	$916.73		$977.6567	$977.66	$977.65	$977.60