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	$41.59	10.708%	$46.0435	$46.04	$46.05	$46.00
Purchase #2	$126.92	12.814%	$143.1835	$143.18	$143.20	$143.20
Purchase #3	$70.49	10.809%	$78.1093	$78.11	$78.10	$78.10
Purchase #4	$181.43	8.449%	$196.759	$196.76	$196.75	$196.80
Purchase #5	$195.53	10.151%	$215.3783	$215.38	$215.40	$215.40
Purchase #6	$23.66	9.724%	$25.9607	$25.96	$25.95	$26.00
Purchase #7	$31.45	11.793%	$35.1589	$35.16	$35.15	$35.20
7 purchase totals =	$671.07		$740.5932	$740.59	$740.60	$740.70