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	$82.36	12.417%	$92.5866	$92.59	$92.60	$92.60
Purchase #2	$205.81	7.557%	$221.3631	$221.36	$221.35	$221.40
Purchase #3	$163.26	10.347%	$180.1525	$180.15	$180.15	$180.20
Purchase #4	$49.76	5.302%	$52.3983	$52.40	$52.40	$52.40
Purchase #5	$148.57	11.274%	$165.3198	$165.32	$165.30	$165.30
Purchase #6	$30.39	8.767%	$33.0543	$33.05	$33.05	$33.10
Purchase #7	$81.68	4.446%	$85.3115	$85.31	$85.30	$85.30
7 purchase totals =	$761.83		$830.1861	$830.18	$830.15	$830.30