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	$191.75	9.819%	$210.5779	$210.58	$210.60	$210.60
Purchase #2	$76.74	12.864%	$86.6118	$86.61	$86.60	$86.60
Purchase #3	$202.45	13.519%	$229.8192	$229.82	$229.80	$229.80
Purchase #4	$178.81	4.680%	$187.1783	$187.18	$187.20	$187.20
Purchase #5	$45.75	7.747%	$49.2943	$49.29	$49.30	$49.30
Purchase #6	$196.96	13.131%	$222.8228	$222.82	$222.80	$222.80
Purchase #7	$166.55	5.592%	$175.8635	$175.86	$175.85	$175.90
7 purchase totals =	$1,059.01		$1,162.1678	$1,162.16	$1,162.15	$1,162.20