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	$82.96	7.583%	$89.2509	$89.25	$89.25	$89.30
Purchase #2	$99.97	12.185%	$112.1513	$112.15	$112.15	$112.20
Purchase #3	$245.67	9.435%	$268.849	$268.85	$268.85	$268.80
Purchase #4	$145.27	5.846%	$153.7625	$153.76	$153.75	$153.80
Purchase #5	$104.79	4.217%	$109.209	$109.21	$109.20	$109.20
Purchase #6	$87.57	6.634%	$93.3794	$93.38	$93.40	$93.40
Purchase #7	$207.34	13.360%	$235.0406	$235.04	$235.05	$235.00
7 purchase totals =	$973.57		$1,061.6427	$1,061.64	$1,061.65	$1,061.70