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	$42.49	4.725%	$44.4977	$44.50	$44.50	$44.50
Purchase #2	$67.83	7.327%	$72.7999	$72.80	$72.80	$72.80
Purchase #3	$148.91	11.401%	$165.8872	$165.89	$165.90	$165.90
Purchase #4	$167.25	12.604%	$188.3302	$188.33	$188.35	$188.30
Purchase #5	$16.81	4.516%	$17.5691	$17.57	$17.55	$17.60
Purchase #6	$70.65	3.225%	$72.9285	$72.93	$72.95	$72.90
Purchase #7	$176.54	7.207%	$189.2632	$189.26	$189.25	$189.30
7 purchase totals =	$690.48		$751.2758	$751.28	$751.30	$751.30