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	$71.53	9.345%	$78.2145	$78.21	$78.20	$78.20
Purchase #2	$28.80	9.820%	$31.6282	$31.63	$31.65	$31.60
Purchase #3	$90.90	3.578%	$94.1524	$94.15	$94.15	$94.20
Purchase #4	$209.82	13.787%	$238.7479	$238.75	$238.75	$238.70
Purchase #5	$226.43	12.138%	$253.9141	$253.91	$253.90	$253.90
Purchase #6	$228.51	8.646%	$248.267	$248.27	$248.25	$248.30
Purchase #7	$60.30	4.368%	$62.9339	$62.93	$62.95	$62.90
7 purchase totals =	$916.29		$1,007.8580	$1,007.85	$1,007.85	$1,007.80