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	$184.63	6.678%	$196.9596	$196.96	$196.95	$197.00
Purchase #2	$36.72	12.486%	$41.3049	$41.30	$41.30	$41.30
Purchase #3	$53.40	11.852%	$59.729	$59.73	$59.75	$59.70
Purchase #4	$92.25	12.255%	$103.5552	$103.56	$103.55	$103.60
Purchase #5	$193.39	3.382%	$199.9304	$199.93	$199.95	$199.90
Purchase #6	$234.61	11.386%	$261.3227	$261.32	$261.30	$261.30
Purchase #7	$5.54	12.745%	$6.2461	$6.25	$6.25	$6.20
7 purchase totals =	$800.54		$869.0479	$869.05	$869.05	$869.00