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	$55.52	12.279%	$62.3373	$62.34	$62.35	$62.30
Purchase #2	$171.57	6.854%	$183.3294	$183.33	$183.35	$183.30
Purchase #3	$199.58	10.151%	$219.8394	$219.84	$219.85	$219.80
Purchase #4	$115.29	10.305%	$127.1706	$127.17	$127.15	$127.20
Purchase #5	$172.94	10.234%	$190.6387	$190.64	$190.65	$190.60
Purchase #6	$124.98	3.199%	$128.9781	$128.98	$129.00	$129.00
Purchase #7	$140.71	10.557%	$155.5648	$155.56	$155.55	$155.60
7 purchase totals =	$980.59		$1,067.8583	$1,067.86	$1,067.90	$1,067.80