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	$201.88	10.846%	$223.7759	$223.78	$223.80	$223.80
Purchase #2	$241.97	3.466%	$250.3567	$250.36	$250.35	$250.40
Purchase #3	$66.87	5.767%	$70.7264	$70.73	$70.75	$70.70
Purchase #4	$249.99	7.807%	$269.5067	$269.51	$269.50	$269.50
Purchase #5	$153.37	12.612%	$172.713	$172.71	$172.70	$172.70
Purchase #6	$84.86	6.460%	$90.342	$90.34	$90.35	$90.30
Purchase #7	$37.84	5.481%	$39.914	$39.91	$39.90	$39.90
7 purchase totals =	$1,036.78		$1,117.3347	$1,117.34	$1,117.35	$1,117.30