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	$53.82	10.225%	$59.3231	$59.32	$59.30	$59.30
Purchase #2	$106.33	3.133%	$109.6613	$109.66	$109.65	$109.70
Purchase #3	$149.74	6.812%	$159.9403	$159.94	$159.95	$159.90
Purchase #4	$185.99	12.718%	$209.6442	$209.64	$209.65	$209.60
Purchase #5	$177.72	3.385%	$183.7358	$183.74	$183.75	$183.70
Purchase #6	$177.51	13.570%	$201.5981	$201.60	$201.60	$201.60
Purchase #7	$123.44	11.647%	$137.8171	$137.82	$137.80	$137.80
7 purchase totals =	$974.55		$1,061.7199	$1,061.72	$1,061.70	$1,061.60