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	$48.27	8.226%	$52.2407	$52.24	$52.25	$52.20
Purchase #2	$54.48	12.127%	$61.0868	$61.09	$61.10	$61.10
Purchase #3	$47.38	6.307%	$50.3683	$50.37	$50.35	$50.40
Purchase #4	$161.36	9.148%	$176.1212	$176.12	$176.10	$176.10
Purchase #5	$64.86	11.597%	$72.3818	$72.38	$72.40	$72.40
Purchase #6	$87.41	8.753%	$95.061	$95.06	$95.05	$95.10
Purchase #7	$172.77	7.615%	$185.9264	$185.93	$185.95	$185.90
7 purchase totals =	$636.53		$693.1862	$693.19	$693.20	$693.20