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	$151.81	10.290%	$167.4312	$167.43	$167.45	$167.40
Purchase #2	$223.60	6.368%	$237.8388	$237.84	$237.85	$237.80
Purchase #3	$129.72	4.505%	$135.5639	$135.56	$135.55	$135.60
Purchase #4	$214.39	7.172%	$229.7661	$229.77	$229.75	$229.80
Purchase #5	$77.72	3.322%	$80.3019	$80.30	$80.30	$80.30
Purchase #6	$78.86	11.301%	$87.772	$87.77	$87.75	$87.80
Purchase #7	$100.56	10.755%	$111.3752	$111.38	$111.40	$111.40
7 purchase totals =	$976.66		$1,050.0491	$1,050.05	$1,050.05	$1,050.10