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	$188.81	4.296%	$196.9213	$196.92	$196.90	$196.90
Purchase #2	$198.70	12.573%	$223.6826	$223.68	$223.70	$223.70
Purchase #3	$148.86	7.442%	$159.9382	$159.94	$159.95	$159.90
Purchase #4	$166.89	3.270%	$172.3473	$172.35	$172.35	$172.30
Purchase #5	$215.33	8.544%	$233.7278	$233.73	$233.75	$233.70
Purchase #6	$188.85	3.167%	$194.8309	$194.83	$194.85	$194.80
Purchase #7	$223.42	8.627%	$242.6944	$242.69	$242.70	$242.70
7 purchase totals =	$1,330.86		$1,424.1425	$1,424.14	$1,424.20	$1,424.00