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	$114.64	3.216%	$118.3268	$118.33	$118.35	$118.30
Purchase #2	$137.72	9.763%	$151.1656	$151.17	$151.15	$151.20
Purchase #3	$99.77	5.242%	$104.9999	$105.00	$105.00	$105.00
Purchase #4	$175.31	6.173%	$186.1319	$186.13	$186.15	$186.10
Purchase #5	$50.31	9.424%	$55.0512	$55.05	$55.05	$55.10
Purchase #6	$228.78	5.783%	$242.0103	$242.01	$242.00	$242.00
Purchase #7	$213.89	10.278%	$235.8736	$235.87	$235.85	$235.90
7 purchase totals =	$1,020.42		$1,093.5593	$1,093.56	$1,093.55	$1,093.60