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	$142.87	13.676%	$162.4089	$162.41	$162.40	$162.40
Purchase #2	$213.44	11.666%	$238.3399	$238.34	$238.35	$238.30
Purchase #3	$119.64	3.688%	$124.0523	$124.05	$124.05	$124.10
Purchase #4	$105.28	11.540%	$117.4293	$117.43	$117.45	$117.40
Purchase #5	$158.30	7.683%	$170.4622	$170.46	$170.45	$170.50
Purchase #6	$176.71	8.499%	$191.7286	$191.73	$191.75	$191.70
Purchase #7	$84.46	6.192%	$89.6898	$89.69	$89.70	$89.70
7 purchase totals =	$1,000.70		$1,094.1110	$1,094.11	$1,094.15	$1,094.10