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	$72.75	7.696%	$78.3488	$78.35	$78.35	$78.30
Purchase #2	$67.34	13.659%	$76.538	$76.54	$76.55	$76.50
Purchase #3	$226.34	6.780%	$241.6859	$241.69	$241.70	$241.70
Purchase #4	$105.63	6.259%	$112.2414	$112.24	$112.25	$112.20
Purchase #5	$206.93	12.192%	$232.1589	$232.16	$232.15	$232.20
Purchase #6	$66.27	8.264%	$71.7466	$71.75	$71.75	$71.70
Purchase #7	$104.58	6.649%	$111.5335	$111.53	$111.55	$111.50
7 purchase totals =	$849.84		$924.2531	$924.26	$924.30	$924.10