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	$107.88	3.741%	$111.9158	$111.92	$111.90	$111.90
Purchase #2	$56.28	10.755%	$62.3329	$62.33	$62.35	$62.30
Purchase #3	$28.88	5.710%	$30.529	$30.53	$30.55	$30.50
Purchase #4	$218.67	11.623%	$244.086	$244.09	$244.10	$244.10
Purchase #5	$106.62	5.615%	$112.6067	$112.61	$112.60	$112.60
Purchase #6	$41.42	4.179%	$43.1509	$43.15	$43.15	$43.20
Purchase #7	$89.49	7.784%	$96.4559	$96.46	$96.45	$96.50
7 purchase totals =	$649.24		$701.0772	$701.09	$701.10	$701.10