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	$237.39	4.308%	$247.6168	$247.62	$247.60	$247.60
Purchase #2	$164.34	12.814%	$185.3985	$185.40	$185.40	$185.40
Purchase #3	$170.72	9.568%	$187.0545	$187.05	$187.05	$187.10
Purchase #4	$174.87	8.549%	$189.8196	$189.82	$189.80	$189.80
Purchase #5	$95.51	4.284%	$99.6016	$99.60	$99.60	$99.60
Purchase #6	$73.47	12.807%	$82.8793	$82.88	$82.90	$82.90
Purchase #7	$165.54	11.276%	$184.2063	$184.21	$184.20	$184.20
7 purchase totals =	$1,081.84		$1,176.5766	$1,176.58	$1,176.55	$1,176.60