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	$95.42	11.684%	$106.5689	$106.57	$106.55	$106.60
Purchase #2	$225.64	3.586%	$233.7315	$233.73	$233.75	$233.70
Purchase #3	$186.61	5.272%	$196.4481	$196.45	$196.45	$196.40
Purchase #4	$150.45	7.756%	$162.1189	$162.12	$162.10	$162.10
Purchase #5	$120.36	10.630%	$133.1543	$133.15	$133.15	$133.20
Purchase #6	$138.36	12.260%	$155.3229	$155.32	$155.30	$155.30
Purchase #7	$185.72	7.615%	$199.8626	$199.86	$199.85	$199.90
7 purchase totals =	$1,102.56		$1,187.2072	$1,187.20	$1,187.15	$1,187.20