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	$155.60	4.149%	$162.0558	$162.06	$162.05	$162.10
Purchase #2	$31.25	3.501%	$32.3441	$32.34	$32.35	$32.30
Purchase #3	$145.63	8.600%	$158.1542	$158.15	$158.15	$158.20
Purchase #4	$246.82	13.145%	$279.2645	$279.26	$279.25	$279.30
Purchase #5	$191.32	6.353%	$203.4746	$203.47	$203.45	$203.50
Purchase #6	$181.33	8.335%	$196.4439	$196.44	$196.45	$196.40
Purchase #7	$218.69	13.200%	$247.5571	$247.56	$247.55	$247.60
7 purchase totals =	$1,170.64		$1,279.2942	$1,279.28	$1,279.25	$1,279.40