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	$72.79	13.199%	$82.3976	$82.40	$82.40	$82.40
Purchase #2	$109.91	4.231%	$114.5603	$114.56	$114.55	$114.60
Purchase #3	$56.30	9.576%	$61.6913	$61.69	$61.70	$61.70
Purchase #4	$90.91	6.571%	$96.8837	$96.88	$96.90	$96.90
Purchase #5	$79.99	11.424%	$89.1281	$89.13	$89.15	$89.10
Purchase #6	$135.52	5.634%	$143.1552	$143.16	$143.15	$143.20
Purchase #7	$101.96	11.249%	$113.4295	$113.43	$113.45	$113.40
7 purchase totals =	$647.38		$701.2457	$701.25	$701.30	$701.30