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	$56.73	9.142%	$61.9163	$61.92	$61.90	$61.90
Purchase #2	$222.82	8.236%	$241.1715	$241.17	$241.15	$241.20
Purchase #3	$62.90	9.341%	$68.7755	$68.78	$68.80	$68.80
Purchase #4	$215.39	6.855%	$230.155	$230.16	$230.15	$230.20
Purchase #5	$116.44	6.112%	$123.5568	$123.56	$123.55	$123.60
Purchase #6	$68.69	4.376%	$71.6959	$71.70	$71.70	$71.70
Purchase #7	$218.70	10.827%	$242.3786	$242.38	$242.40	$242.40
7 purchase totals =	$961.67		$1,039.6496	$1,039.67	$1,039.65	$1,039.80