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	$101.77	7.430%	$109.3315	$109.33	$109.35	$109.30
Purchase #2	$141.54	13.376%	$160.4724	$160.47	$160.45	$160.50
Purchase #3	$65.90	9.342%	$72.0564	$72.06	$72.05	$72.10
Purchase #4	$184.85	5.711%	$195.4068	$195.41	$195.40	$195.40
Purchase #5	$174.42	3.680%	$180.8387	$180.84	$180.85	$180.80
Purchase #6	$234.28	3.500%	$242.4798	$242.48	$242.50	$242.50
Purchase #7	$196.59	4.649%	$205.7295	$205.73	$205.75	$205.70
7 purchase totals =	$1,099.35		$1,166.3151	$1,166.32	$1,166.35	$1,166.30