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	$235.37	7.674%	$253.4323	$253.43	$253.45	$253.40
Purchase #2	$74.27	4.302%	$77.4651	$77.47	$77.45	$77.50
Purchase #3	$156.61	7.228%	$167.9298	$167.93	$167.95	$167.90
Purchase #4	$188.88	8.164%	$204.3002	$204.30	$204.30	$204.30
Purchase #5	$250.66	3.497%	$259.4256	$259.43	$259.45	$259.40
Purchase #6	$212.28	3.166%	$219.0008	$219.00	$219.00	$219.00
Purchase #7	$90.36	11.666%	$100.9014	$100.90	$100.90	$100.90
7 purchase totals =	$1,208.43		$1,282.4552	$1,282.46	$1,282.50	$1,282.40