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	$247.83	13.839%	$282.1272	$282.13	$282.15	$282.10
Purchase #2	$186.88	3.833%	$194.0431	$194.04	$194.05	$194.00
Purchase #3	$36.61	7.568%	$39.3806	$39.38	$39.40	$39.40
Purchase #4	$169.57	9.138%	$185.0653	$185.07	$185.05	$185.10
Purchase #5	$174.67	6.428%	$185.8978	$185.90	$185.90	$185.90
Purchase #6	$122.54	5.788%	$129.6326	$129.63	$129.65	$129.60
Purchase #7	$175.26	3.146%	$180.7737	$180.77	$180.75	$180.80
7 purchase totals =	$1,113.36		$1,196.9203	$1,196.92	$1,196.95	$1,196.90