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	$41.56	7.668%	$44.7468	$44.75	$44.75	$44.70
Purchase #2	$74.37	6.104%	$78.9095	$78.91	$78.90	$78.90
Purchase #3	$116.75	9.264%	$127.5657	$127.57	$127.55	$127.60
Purchase #4	$175.67	7.132%	$188.1988	$188.20	$188.20	$188.20
Purchase #5	$197.31	11.291%	$219.5883	$219.59	$219.60	$219.60
Purchase #6	$135.89	7.170%	$145.6333	$145.63	$145.65	$145.60
Purchase #7	$112.47	6.231%	$119.478	$119.48	$119.50	$119.50
7 purchase totals =	$854.02		$924.1204	$924.13	$924.15	$924.10