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	$196.38	13.311%	$222.5201	$222.52	$222.50	$222.50
Purchase #2	$86.44	5.332%	$91.049	$91.05	$91.05	$91.00
Purchase #3	$96.84	7.102%	$103.7176	$103.72	$103.70	$103.70
Purchase #4	$46.77	8.573%	$50.7796	$50.78	$50.80	$50.80
Purchase #5	$212.31	8.302%	$229.936	$229.94	$229.95	$229.90
Purchase #6	$6.48	11.616%	$7.2327	$7.23	$7.25	$7.20
Purchase #7	$62.88	10.253%	$69.3271	$69.33	$69.35	$69.30
7 purchase totals =	$708.10		$774.5621	$774.57	$774.60	$774.40