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	$115.42	8.530%	$125.2653	$125.27	$125.25	$125.30
Purchase #2	$110.89	6.751%	$118.3762	$118.38	$118.40	$118.40
Purchase #3	$189.37	12.382%	$212.8178	$212.82	$212.80	$212.80
Purchase #4	$39.77	13.292%	$45.0562	$45.06	$45.05	$45.10
Purchase #5	$196.26	13.799%	$223.3419	$223.34	$223.35	$223.30
Purchase #6	$156.91	8.697%	$170.5565	$170.56	$170.55	$170.60
Purchase #7	$180.53	4.155%	$188.031	$188.03	$188.05	$188.00
7 purchase totals =	$989.15		$1,083.4449	$1,083.46	$1,083.45	$1,083.50