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	$219.79	3.502%	$227.487	$227.49	$227.50	$227.50
Purchase #2	$35.31	11.780%	$39.4695	$39.47	$39.45	$39.50
Purchase #3	$218.29	8.458%	$236.753	$236.75	$236.75	$236.80
Purchase #4	$88.51	13.334%	$100.3119	$100.31	$100.30	$100.30
Purchase #5	$174.72	12.412%	$196.4062	$196.41	$196.40	$196.40
Purchase #6	$152.97	4.515%	$159.8766	$159.88	$159.90	$159.90
Purchase #7	$249.59	5.773%	$263.9988	$264.00	$264.00	$264.00
7 purchase totals =	$1,139.18		$1,224.3030	$1,224.31	$1,224.30	$1,224.40