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	$169.52	11.626%	$189.2284	$189.23	$189.25	$189.20
Purchase #2	$96.81	3.134%	$99.844	$99.84	$99.85	$99.80
Purchase #3	$50.91	13.598%	$57.8327	$57.83	$57.85	$57.80
Purchase #4	$147.31	13.717%	$167.5165	$167.52	$167.50	$167.50
Purchase #5	$91.25	4.490%	$95.3471	$95.35	$95.35	$95.30
Purchase #6	$119.90	7.640%	$129.0604	$129.06	$129.05	$129.10
Purchase #7	$19.40	5.836%	$20.5322	$20.53	$20.55	$20.50
7 purchase totals =	$695.10		$759.3613	$759.36	$759.40	$759.20