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	$99.68	4.498%	$104.1636	$104.16	$104.15	$104.20
Purchase #2	$124.33	7.415%	$133.5491	$133.55	$133.55	$133.50
Purchase #3	$136.61	7.706%	$147.1372	$147.14	$147.15	$147.10
Purchase #4	$96.75	8.656%	$105.1247	$105.12	$105.10	$105.10
Purchase #5	$13.26	3.712%	$13.7522	$13.75	$13.75	$13.80
Purchase #6	$180.31	11.236%	$200.5696	$200.57	$200.55	$200.60
Purchase #7	$154.83	6.680%	$165.1726	$165.17	$165.15	$165.20
7 purchase totals =	$805.77		$869.4690	$869.46	$869.40	$869.50