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	$161.38	6.445%	$171.7809	$171.78	$171.80	$171.80
Purchase #2	$127.81	3.129%	$131.8092	$131.81	$131.80	$131.80
Purchase #3	$159.57	13.809%	$181.605	$181.61	$181.60	$181.60
Purchase #4	$33.68	4.151%	$35.0781	$35.08	$35.10	$35.10
Purchase #5	$182.60	8.740%	$198.5592	$198.56	$198.55	$198.60
Purchase #6	$107.41	11.855%	$120.1435	$120.14	$120.15	$120.10
Purchase #7	$165.45	8.125%	$178.8928	$178.89	$178.90	$178.90
7 purchase totals =	$937.90		$1,017.8687	$1,017.87	$1,017.90	$1,017.90