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	$250.40	6.244%	$266.035	$266.04	$266.05	$266.00
Purchase #2	$212.27	3.360%	$219.4023	$219.40	$219.40	$219.40
Purchase #3	$170.67	11.486%	$190.2732	$190.27	$190.25	$190.30
Purchase #4	$184.62	9.610%	$202.362	$202.36	$202.35	$202.40
Purchase #5	$115.83	10.352%	$127.8207	$127.82	$127.80	$127.80
Purchase #6	$32.97	12.231%	$37.0026	$37.00	$37.00	$37.00
Purchase #7	$35.65	3.805%	$37.0065	$37.01	$37.00	$37.00
7 purchase totals =	$1,002.41		$1,079.9023	$1,079.90	$1,079.85	$1,079.90