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	$59.74	12.459%	$67.183	$67.18	$67.20	$67.20
Purchase #2	$114.48	5.650%	$120.9481	$120.95	$120.95	$120.90
Purchase #3	$178.27	5.360%	$187.8253	$187.83	$187.85	$187.80
Purchase #4	$244.58	3.774%	$253.8104	$253.81	$253.80	$253.80
Purchase #5	$85.35	3.836%	$88.624	$88.62	$88.60	$88.60
Purchase #6	$243.72	11.432%	$271.5821	$271.58	$271.60	$271.60
Purchase #7	$151.29	7.377%	$162.4507	$162.45	$162.45	$162.50
7 purchase totals =	$1,077.43		$1,152.4236	$1,152.42	$1,152.45	$1,152.40