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	$96.88	13.168%	$109.6372	$109.64	$109.65	$109.60
Purchase #2	$89.39	11.162%	$99.3677	$99.37	$99.35	$99.40
Purchase #3	$132.75	11.792%	$148.4039	$148.40	$148.40	$148.40
Purchase #4	$211.60	8.307%	$229.1776	$229.18	$229.20	$229.20
Purchase #5	$196.93	10.728%	$218.0567	$218.06	$218.05	$218.10
Purchase #6	$108.77	6.396%	$115.7269	$115.73	$115.75	$115.70
Purchase #7	$181.36	5.465%	$191.2713	$191.27	$191.25	$191.30
7 purchase totals =	$1,017.68		$1,111.6413	$1,111.65	$1,111.65	$1,111.70