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	$100.55	4.560%	$105.1351	$105.14	$105.15	$105.10
Purchase #2	$242.78	10.644%	$268.6215	$268.62	$268.60	$268.60
Purchase #3	$73.58	6.448%	$78.3244	$78.32	$78.30	$78.30
Purchase #4	$172.43	3.204%	$177.9547	$177.95	$177.95	$178.00
Purchase #5	$82.98	8.243%	$89.82	$89.82	$89.80	$89.80
Purchase #6	$50.73	12.708%	$57.1768	$57.18	$57.20	$57.20
Purchase #7	$249.31	7.362%	$267.6642	$267.66	$267.65	$267.70
7 purchase totals =	$972.36		$1,044.6967	$1,044.69	$1,044.65	$1,044.70