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	$54.34	7.665%	$58.5052	$58.51	$58.50	$58.50
Purchase #2	$70.75	13.289%	$80.152	$80.15	$80.15	$80.20
Purchase #3	$75.76	13.756%	$86.1815	$86.18	$86.20	$86.20
Purchase #4	$187.53	12.287%	$210.5718	$210.57	$210.55	$210.60
Purchase #5	$149.95	11.281%	$166.8659	$166.87	$166.85	$166.90
Purchase #6	$200.56	5.338%	$211.2659	$211.27	$211.25	$211.30
Purchase #7	$80.80	12.489%	$90.8911	$90.89	$90.90	$90.90
7 purchase totals =	$819.69		$904.4334	$904.44	$904.40	$904.60