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	$66.81	7.737%	$71.9791	$71.98	$72.00	$72.00
Purchase #2	$184.91	7.498%	$198.7746	$198.77	$198.75	$198.80
Purchase #3	$15.81	12.151%	$17.7311	$17.73	$17.75	$17.70
Purchase #4	$191.39	7.364%	$205.484	$205.48	$205.50	$205.50
Purchase #5	$78.79	4.549%	$82.3742	$82.37	$82.35	$82.40
Purchase #6	$247.41	12.335%	$277.928	$277.93	$277.95	$277.90
Purchase #7	$63.39	13.752%	$72.1074	$72.11	$72.10	$72.10
7 purchase totals =	$848.51		$926.3784	$926.37	$926.40	$926.40