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	$58.85	4.130%	$61.2805	$61.28	$61.30	$61.30
Purchase #2	$142.84	9.699%	$156.6941	$156.69	$156.70	$156.70
Purchase #3	$105.55	4.508%	$110.3082	$110.31	$110.30	$110.30
Purchase #4	$101.56	3.679%	$105.2964	$105.30	$105.30	$105.30
Purchase #5	$80.75	11.241%	$89.8271	$89.83	$89.85	$89.80
Purchase #6	$212.86	4.865%	$223.2156	$223.22	$223.20	$223.20
Purchase #7	$200.80	13.742%	$228.3939	$228.39	$228.40	$228.40
7 purchase totals =	$903.21		$975.0158	$975.02	$975.05	$975.00