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	$192.69	10.228%	$212.3983	$212.40	$212.40	$212.40
Purchase #2	$80.85	3.755%	$83.8859	$83.89	$83.90	$83.90
Purchase #3	$167.72	10.343%	$185.0673	$185.07	$185.05	$185.10
Purchase #4	$16.38	11.137%	$18.2042	$18.20	$18.20	$18.20
Purchase #5	$161.79	6.608%	$172.4811	$172.48	$172.50	$172.50
Purchase #6	$88.28	11.345%	$98.2954	$98.30	$98.30	$98.30
Purchase #7	$38.94	3.711%	$40.3851	$40.39	$40.40	$40.40
7 purchase totals =	$746.65		$810.7173	$810.73	$810.75	$810.80