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	$62.80	13.139%	$71.0513	$71.05	$71.05	$71.10
Purchase #2	$196.63	6.293%	$209.0039	$209.00	$209.00	$209.00
Purchase #3	$79.67	4.122%	$82.954	$82.95	$82.95	$83.00
Purchase #4	$12.64	13.354%	$14.3279	$14.33	$14.35	$14.30
Purchase #5	$249.64	7.624%	$268.6726	$268.67	$268.65	$268.70
Purchase #6	$69.28	13.669%	$78.7499	$78.75	$78.75	$78.70
Purchase #7	$232.39	10.221%	$256.1426	$256.14	$256.15	$256.10
7 purchase totals =	$903.05		$980.9022	$980.89	$980.90	$980.90