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	$236.63	4.552%	$247.4014	$247.40	$247.40	$247.40
Purchase #2	$173.81	4.726%	$182.0243	$182.02	$182.00	$182.00
Purchase #3	$99.63	13.742%	$113.3212	$113.32	$113.30	$113.30
Purchase #4	$84.93	4.477%	$88.7323	$88.73	$88.75	$88.70
Purchase #5	$135.61	11.336%	$150.9827	$150.98	$151.00	$151.00
Purchase #6	$92.42	7.650%	$99.4901	$99.49	$99.50	$99.50
Purchase #7	$170.69	6.845%	$182.3737	$182.37	$182.35	$182.40
7 purchase totals =	$993.72		$1,064.3257	$1,064.31	$1,064.30	$1,064.30