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	$82.61	11.429%	$92.0515	$92.05	$92.05	$92.10
Purchase #2	$159.64	9.516%	$174.8313	$174.83	$174.85	$174.80
Purchase #3	$223.76	7.398%	$240.3138	$240.31	$240.30	$240.30
Purchase #4	$38.39	5.431%	$40.475	$40.48	$40.50	$40.50
Purchase #5	$135.39	9.257%	$147.9231	$147.92	$147.90	$147.90
Purchase #6	$242.52	7.304%	$260.2337	$260.23	$260.25	$260.20
Purchase #7	$77.98	5.773%	$82.4818	$82.48	$82.50	$82.50
7 purchase totals =	$960.29		$1,038.3102	$1,038.30	$1,038.35	$1,038.30