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	$68.61	4.601%	$71.7667	$71.77	$71.75	$71.80
Purchase #2	$30.73	4.452%	$32.0981	$32.10	$32.10	$32.10
Purchase #3	$76.72	13.662%	$87.2015	$87.20	$87.20	$87.20
Purchase #4	$187.83	3.581%	$194.5562	$194.56	$194.55	$194.60
Purchase #5	$50.75	9.412%	$55.5266	$55.53	$55.55	$55.50
Purchase #6	$166.64	11.242%	$185.3737	$185.37	$185.35	$185.40
Purchase #7	$65.95	12.305%	$74.0651	$74.07	$74.05	$74.10
7 purchase totals =	$647.23		$700.5879	$700.60	$700.55	$700.70