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	$157.31	11.772%	$175.8285	$175.83	$175.85	$175.80
Purchase #2	$55.66	7.465%	$59.815	$59.82	$59.80	$59.80
Purchase #3	$66.55	13.125%	$75.2847	$75.28	$75.30	$75.30
Purchase #4	$136.56	4.468%	$142.6615	$142.66	$142.65	$142.70
Purchase #5	$226.46	12.267%	$254.2398	$254.24	$254.25	$254.20
Purchase #6	$75.58	8.865%	$82.2802	$82.28	$82.30	$82.30
Purchase #7	$116.61	9.522%	$127.7136	$127.71	$127.70	$127.70
7 purchase totals =	$834.73		$917.8233	$917.82	$917.85	$917.80