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	$221.69	8.762%	$241.1145	$241.11	$241.10	$241.10
Purchase #2	$64.91	8.511%	$70.4345	$70.43	$70.45	$70.40
Purchase #3	$136.25	4.873%	$142.8895	$142.89	$142.90	$142.90
Purchase #4	$137.85	5.138%	$144.9327	$144.93	$144.95	$144.90
Purchase #5	$70.64	4.410%	$73.7552	$73.76	$73.75	$73.80
Purchase #6	$99.58	13.523%	$113.0462	$113.05	$113.05	$113.00
Purchase #7	$79.30	5.473%	$83.6401	$83.64	$83.65	$83.60
7 purchase totals =	$810.22		$869.8127	$869.81	$869.85	$869.70