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	$231.61	4.314%	$241.6017	$241.60	$241.60	$241.60
Purchase #2	$54.72	10.234%	$60.32	$60.32	$60.30	$60.30
Purchase #3	$89.95	7.872%	$97.0309	$97.03	$97.05	$97.00
Purchase #4	$80.37	11.794%	$89.8488	$89.85	$89.85	$89.80
Purchase #5	$202.79	10.399%	$223.8781	$223.88	$223.90	$223.90
Purchase #6	$117.37	10.355%	$129.5237	$129.52	$129.50	$129.50
Purchase #7	$47.91	10.302%	$52.8457	$52.85	$52.85	$52.80
7 purchase totals =	$824.72		$895.0489	$895.05	$895.05	$894.90