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	$132.43	11.273%	$147.3588	$147.36	$147.35	$147.40
Purchase #2	$72.50	13.650%	$82.3963	$82.40	$82.40	$82.40
Purchase #3	$14.29	6.794%	$15.2609	$15.26	$15.25	$15.30
Purchase #4	$181.50	8.117%	$196.2324	$196.23	$196.25	$196.20
Purchase #5	$232.75	4.104%	$242.3021	$242.30	$242.30	$242.30
Purchase #6	$146.56	4.865%	$153.6901	$153.69	$153.70	$153.70
Purchase #7	$155.83	4.371%	$162.6413	$162.64	$162.65	$162.60
7 purchase totals =	$935.86		$999.8819	$999.88	$999.90	$999.90