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	$64.56	13.612%	$73.3479	$73.35	$73.35	$73.30
Purchase #2	$78.37	5.744%	$82.8716	$82.87	$82.85	$82.90
Purchase #3	$142.75	6.283%	$151.719	$151.72	$151.70	$151.70
Purchase #4	$133.61	12.378%	$150.1482	$150.15	$150.15	$150.10
Purchase #5	$248.53	9.272%	$271.5737	$271.57	$271.55	$271.60
Purchase #6	$148.60	9.133%	$162.1716	$162.17	$162.15	$162.20
Purchase #7	$170.82	10.346%	$188.493	$188.49	$188.50	$188.50
7 purchase totals =	$987.24		$1,080.3250	$1,080.32	$1,080.25	$1,080.30