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	$200.77	11.131%	$223.1177	$223.12	$223.10	$223.10
Purchase #2	$46.78	7.505%	$50.2908	$50.29	$50.30	$50.30
Purchase #3	$73.36	12.676%	$82.6591	$82.66	$82.65	$82.70
Purchase #4	$193.89	9.140%	$211.6115	$211.61	$211.60	$211.60
Purchase #5	$27.86	12.230%	$31.2673	$31.27	$31.25	$31.30
Purchase #6	$246.31	5.711%	$260.3768	$260.38	$260.40	$260.40
Purchase #7	$250.87	6.218%	$266.4691	$266.47	$266.45	$266.50
7 purchase totals =	$1,039.84		$1,125.7923	$1,125.80	$1,125.75	$1,125.90