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	$162.83	5.533%	$171.8394	$171.84	$171.85	$171.80
Purchase #2	$207.66	13.544%	$235.7855	$235.79	$235.80	$235.80
Purchase #3	$31.93	12.467%	$35.9107	$35.91	$35.90	$35.90
Purchase #4	$67.61	6.244%	$71.8316	$71.83	$71.85	$71.80
Purchase #5	$153.88	8.622%	$167.1475	$167.15	$167.15	$167.10
Purchase #6	$172.43	10.402%	$190.3662	$190.37	$190.35	$190.40
Purchase #7	$47.53	5.768%	$50.2715	$50.27	$50.25	$50.30
7 purchase totals =	$843.87		$923.1524	$923.16	$923.15	$923.10