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	$100.52	11.444%	$112.0235	$112.02	$112.00	$112.00
Purchase #2	$120.55	11.694%	$134.6471	$134.65	$134.65	$134.60
Purchase #3	$33.42	6.314%	$35.5301	$35.53	$35.55	$35.50
Purchase #4	$89.49	12.104%	$100.3219	$100.32	$100.30	$100.30
Purchase #5	$66.26	7.590%	$71.2891	$71.29	$71.30	$71.30
Purchase #6	$196.53	7.724%	$211.71	$211.71	$211.70	$211.70
Purchase #7	$120.49	7.174%	$129.134	$129.13	$129.15	$129.10
7 purchase totals =	$727.26		$794.6557	$794.65	$794.65	$794.50