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	$114.50	11.676%	$127.869	$127.87	$127.85	$127.90
Purchase #2	$165.59	3.758%	$171.8129	$171.81	$171.80	$171.80
Purchase #3	$18.27	10.228%	$20.1387	$20.14	$20.15	$20.10
Purchase #4	$91.45	12.684%	$103.0495	$103.05	$103.05	$103.00
Purchase #5	$89.48	10.618%	$98.981	$98.98	$99.00	$99.00
Purchase #6	$35.42	6.591%	$37.7545	$37.75	$37.75	$37.80
Purchase #7	$44.84	5.409%	$47.2654	$47.27	$47.25	$47.30
7 purchase totals =	$559.55		$606.8710	$606.87	$606.85	$606.90