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	$211.75	5.642%	$223.6969	$223.70	$223.70	$223.70
Purchase #2	$247.26	13.865%	$281.5426	$281.54	$281.55	$281.50
Purchase #3	$109.80	4.501%	$114.7421	$114.74	$114.75	$114.70
Purchase #4	$49.66	12.532%	$55.8834	$55.88	$55.90	$55.90
Purchase #5	$98.91	10.797%	$109.5893	$109.59	$109.60	$109.60
Purchase #6	$198.80	4.873%	$208.4875	$208.49	$208.50	$208.50
Purchase #7	$24.33	3.701%	$25.2305	$25.23	$25.25	$25.20
7 purchase totals =	$940.51		$1,019.1723	$1,019.17	$1,019.25	$1,019.10