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	$147.29	13.558%	$167.2596	$167.26	$167.25	$167.30
Purchase #2	$230.47	4.315%	$240.4148	$240.41	$240.40	$240.40
Purchase #3	$91.90	9.703%	$100.8171	$100.82	$100.80	$100.80
Purchase #4	$218.57	11.145%	$242.9296	$242.93	$242.95	$242.90
Purchase #5	$80.29	3.745%	$83.2969	$83.30	$83.30	$83.30
Purchase #6	$204.79	3.294%	$211.5358	$211.54	$211.55	$211.50
Purchase #7	$139.66	13.443%	$158.4345	$158.43	$158.45	$158.40
7 purchase totals =	$1,112.97		$1,204.6883	$1,204.69	$1,204.70	$1,204.60