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	$78.93	5.572%	$83.328	$83.33	$83.35	$83.30
Purchase #2	$241.34	11.192%	$268.3508	$268.35	$268.35	$268.40
Purchase #3	$167.62	10.841%	$185.7917	$185.79	$185.80	$185.80
Purchase #4	$20.82	4.822%	$21.8239	$21.82	$21.80	$21.80
Purchase #5	$133.88	5.274%	$140.9408	$140.94	$140.95	$140.90
Purchase #6	$92.70	12.319%	$104.1197	$104.12	$104.10	$104.10
Purchase #7	$188.66	9.283%	$206.1733	$206.17	$206.15	$206.20
7 purchase totals =	$923.95		$1,010.5282	$1,010.52	$1,010.50	$1,010.50