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	$39.38	3.521%	$40.7666	$40.77	$40.75	$40.80
Purchase #2	$71.69	7.726%	$77.2288	$77.23	$77.25	$77.20
Purchase #3	$231.76	4.173%	$241.4313	$241.43	$241.45	$241.40
Purchase #4	$155.57	7.506%	$167.2471	$167.25	$167.25	$167.20
Purchase #5	$171.91	10.126%	$189.3176	$189.32	$189.30	$189.30
Purchase #6	$224.34	13.252%	$254.0695	$254.07	$254.05	$254.10
Purchase #7	$176.46	6.815%	$188.4857	$188.49	$188.50	$188.50
7 purchase totals =	$1,071.11		$1,158.5466	$1,158.56	$1,158.55	$1,158.50