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	$91.41	11.171%	$101.6214	$101.62	$101.60	$101.60
Purchase #2	$124.44	7.871%	$134.2347	$134.23	$134.25	$134.20
Purchase #3	$140.88	6.174%	$149.5779	$149.58	$149.60	$149.60
Purchase #4	$63.28	6.405%	$67.3331	$67.33	$67.35	$67.30
Purchase #5	$86.68	4.851%	$90.8848	$90.88	$90.90	$90.90
Purchase #6	$81.44	4.572%	$85.1634	$85.16	$85.15	$85.20
Purchase #7	$225.99	6.227%	$240.0624	$240.06	$240.05	$240.10
7 purchase totals =	$814.12		$868.8777	$868.86	$868.90	$868.90