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	$73.53	5.287%	$77.4175	$77.42	$77.40	$77.40
Purchase #2	$181.34	10.551%	$200.4732	$200.47	$200.45	$200.50
Purchase #3	$219.37	3.191%	$226.3701	$226.37	$226.35	$226.40
Purchase #4	$87.39	4.594%	$91.4047	$91.40	$91.40	$91.40
Purchase #5	$52.79	3.621%	$54.7015	$54.70	$54.70	$54.70
Purchase #6	$170.86	7.321%	$183.3687	$183.37	$183.35	$183.40
Purchase #7	$218.31	11.711%	$243.8763	$243.88	$243.90	$243.90
7 purchase totals =	$1,003.59		$1,077.6120	$1,077.61	$1,077.55	$1,077.70