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	$113.42	9.218%	$123.8751	$123.88	$123.90	$123.90
Purchase #2	$175.26	7.721%	$188.7918	$188.79	$188.80	$188.80
Purchase #3	$196.33	9.392%	$214.7693	$214.77	$214.75	$214.80
Purchase #4	$19.52	4.510%	$20.4004	$20.40	$20.40	$20.40
Purchase #5	$77.78	10.632%	$86.0496	$86.05	$86.05	$86.00
Purchase #6	$56.57	4.512%	$59.1224	$59.12	$59.10	$59.10
Purchase #7	$92.77	13.202%	$105.0175	$105.02	$105.00	$105.00
7 purchase totals =	$731.65		$798.0261	$798.03	$798.00	$798.00