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	$115.43	6.675%	$123.135	$123.14	$123.15	$123.10
Purchase #2	$202.97	3.109%	$209.2803	$209.28	$209.30	$209.30
Purchase #3	$25.62	7.713%	$27.5961	$27.60	$27.60	$27.60
Purchase #4	$246.83	7.273%	$264.7819	$264.78	$264.80	$264.80
Purchase #5	$85.27	5.846%	$90.2549	$90.25	$90.25	$90.30
Purchase #6	$143.89	7.821%	$155.1436	$155.14	$155.15	$155.10
Purchase #7	$68.58	3.859%	$71.2265	$71.23	$71.25	$71.20
7 purchase totals =	$888.59		$941.4183	$941.42	$941.50	$941.40