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	$210.63	11.829%	$235.5454	$235.55	$235.55	$235.50
Purchase #2	$211.44	10.273%	$233.1612	$233.16	$233.15	$233.20
Purchase #3	$118.86	10.471%	$131.3058	$131.31	$131.30	$131.30
Purchase #4	$123.58	3.397%	$127.778	$127.78	$127.80	$127.80
Purchase #5	$57.64	7.112%	$61.7394	$61.74	$61.75	$61.70
Purchase #6	$7.75	13.506%	$8.7967	$8.80	$8.80	$8.80
Purchase #7	$148.70	10.566%	$164.4116	$164.41	$164.40	$164.40
7 purchase totals =	$878.60		$962.7381	$962.75	$962.75	$962.70