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	$52.63	13.845%	$59.9166	$59.92	$59.90	$59.90
Purchase #2	$47.79	12.781%	$53.898	$53.90	$53.90	$53.90
Purchase #3	$136.55	11.436%	$152.1659	$152.17	$152.15	$152.20
Purchase #4	$159.30	9.506%	$174.4431	$174.44	$174.45	$174.40
Purchase #5	$31.57	8.753%	$34.3333	$34.33	$34.35	$34.30
Purchase #6	$221.88	5.831%	$234.8178	$234.82	$234.80	$234.80
Purchase #7	$29.32	8.106%	$31.6967	$31.70	$31.70	$31.70
7 purchase totals =	$679.04		$741.2714	$741.28	$741.25	$741.20