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	$45.49	4.122%	$47.3651	$47.37	$47.35	$47.40
Purchase #2	$243.90	10.219%	$268.8241	$268.82	$268.80	$268.80
Purchase #3	$99.67	11.667%	$111.2985	$111.30	$111.30	$111.30
Purchase #4	$99.58	13.449%	$112.9725	$112.97	$112.95	$113.00
Purchase #5	$130.86	10.123%	$144.107	$144.11	$144.10	$144.10
Purchase #6	$45.70	3.497%	$47.2981	$47.30	$47.30	$47.30
Purchase #7	$106.29	5.713%	$112.3623	$112.36	$112.35	$112.40
7 purchase totals =	$771.49		$844.2276	$844.23	$844.15	$844.30