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	$145.96	3.289%	$150.7606	$150.76	$150.75	$150.80
Purchase #2	$111.41	6.667%	$118.8377	$118.84	$118.85	$118.80
Purchase #3	$32.91	7.539%	$35.3911	$35.39	$35.40	$35.40
Purchase #4	$42.42	6.488%	$45.1722	$45.17	$45.15	$45.20
Purchase #5	$207.70	5.378%	$218.8701	$218.87	$218.85	$218.90
Purchase #6	$131.59	7.709%	$141.7343	$141.73	$141.75	$141.70
Purchase #7	$62.77	3.234%	$64.8	$64.80	$64.80	$64.80
7 purchase totals =	$734.76		$775.5660	$775.56	$775.55	$775.60