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	$44.41	3.847%	$46.1185	$46.12	$46.10	$46.10
Purchase #2	$156.44	9.641%	$171.5224	$171.52	$171.50	$171.50
Purchase #3	$72.79	5.139%	$76.5307	$76.53	$76.55	$76.50
Purchase #4	$39.98	5.344%	$42.1165	$42.12	$42.10	$42.10
Purchase #5	$196.25	6.202%	$208.4214	$208.42	$208.40	$208.40
Purchase #6	$164.97	6.744%	$176.0956	$176.10	$176.10	$176.10
Purchase #7	$43.75	4.549%	$45.7402	$45.74	$45.75	$45.70
7 purchase totals =	$718.59		$766.5453	$766.55	$766.50	$766.40