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	$75.30	4.313%	$78.5477	$78.55	$78.55	$78.50
Purchase #2	$105.27	13.404%	$119.3804	$119.38	$119.40	$119.40
Purchase #3	$67.88	5.692%	$71.7437	$71.74	$71.75	$71.70
Purchase #4	$18.49	9.811%	$20.3041	$20.30	$20.30	$20.30
Purchase #5	$197.85	4.591%	$206.9333	$206.93	$206.95	$206.90
Purchase #6	$236.68	11.266%	$263.3444	$263.34	$263.35	$263.30
Purchase #7	$51.73	11.375%	$57.6143	$57.61	$57.60	$57.60
7 purchase totals =	$753.20		$817.8679	$817.85	$817.90	$817.70