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	$17.71	7.600%	$19.056	$19.06	$19.05	$19.10
Purchase #2	$217.96	12.173%	$244.4923	$244.49	$244.50	$244.50
Purchase #3	$73.49	6.739%	$78.4425	$78.44	$78.45	$78.40
Purchase #4	$133.41	10.289%	$147.1366	$147.14	$147.15	$147.10
Purchase #5	$127.84	12.303%	$143.5682	$143.57	$143.55	$143.60
Purchase #6	$193.27	6.469%	$205.7726	$205.77	$205.75	$205.80
Purchase #7	$165.85	7.421%	$178.1577	$178.16	$178.15	$178.20
7 purchase totals =	$929.53		$1,016.6259	$1,016.63	$1,016.60	$1,016.70