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	$207.46	11.375%	$231.0586	$231.06	$231.05	$231.10
Purchase #2	$98.46	6.619%	$104.9771	$104.98	$105.00	$105.00
Purchase #3	$238.69	10.477%	$263.6976	$263.70	$263.70	$263.70
Purchase #4	$53.42	8.148%	$57.7727	$57.77	$57.75	$57.80
Purchase #5	$12.44	3.760%	$12.9077	$12.91	$12.90	$12.90
Purchase #6	$65.90	7.822%	$71.0547	$71.05	$71.05	$71.10
Purchase #7	$35.32	12.862%	$39.8629	$39.86	$39.85	$39.90
7 purchase totals =	$711.69		$781.3313	$781.33	$781.30	$781.50