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	$177.45	10.840%	$196.6856	$196.69	$196.70	$196.70
Purchase #2	$79.59	5.315%	$83.8202	$83.82	$83.80	$83.80
Purchase #3	$220.89	11.322%	$245.8992	$245.90	$245.90	$245.90
Purchase #4	$88.64	10.532%	$97.9756	$97.98	$98.00	$98.00
Purchase #5	$15.79	3.443%	$16.3336	$16.33	$16.35	$16.30
Purchase #6	$161.64	6.517%	$172.1741	$172.17	$172.15	$172.20
Purchase #7	$186.76	9.519%	$204.5377	$204.54	$204.55	$204.50
7 purchase totals =	$930.76		$1,017.4260	$1,017.43	$1,017.45	$1,017.40