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	$68.25	7.458%	$73.3401	$73.34	$73.35	$73.30
Purchase #2	$78.83	13.332%	$89.3396	$89.34	$89.35	$89.30
Purchase #3	$82.91	7.364%	$89.0155	$89.02	$89.00	$89.00
Purchase #4	$151.37	4.427%	$158.0711	$158.07	$158.05	$158.10
Purchase #5	$100.57	5.356%	$105.9565	$105.96	$105.95	$106.00
Purchase #6	$193.42	3.667%	$200.5127	$200.51	$200.50	$200.50
Purchase #7	$161.70	5.114%	$169.9693	$169.97	$169.95	$170.00
7 purchase totals =	$837.05		$886.2048	$886.21	$886.15	$886.20