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	$190.42	3.296%	$196.6962	$196.70	$196.70	$196.70
Purchase #2	$117.40	8.575%	$127.4671	$127.47	$127.45	$127.50
Purchase #3	$222.76	9.605%	$244.1561	$244.16	$244.15	$244.20
Purchase #4	$189.74	11.594%	$211.7385	$211.74	$211.75	$211.70
Purchase #5	$248.28	6.688%	$264.885	$264.89	$264.90	$264.90
Purchase #6	$98.86	3.712%	$102.5297	$102.53	$102.55	$102.50
Purchase #7	$141.98	10.518%	$156.9135	$156.91	$156.90	$156.90
7 purchase totals =	$1,209.44		$1,304.3861	$1,304.40	$1,304.40	$1,304.40