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	$203.81	9.381%	$222.9294	$222.93	$222.95	$222.90
Purchase #2	$183.57	7.116%	$196.6328	$196.63	$196.65	$196.60
Purchase #3	$51.84	5.166%	$54.5181	$54.52	$54.50	$54.50
Purchase #4	$206.78	10.754%	$229.0171	$229.02	$229.00	$229.00
Purchase #5	$150.57	13.798%	$171.3456	$171.35	$171.35	$171.30
Purchase #6	$145.48	9.338%	$159.0649	$159.06	$159.05	$159.10
Purchase #7	$150.41	5.314%	$158.4028	$158.40	$158.40	$158.40
7 purchase totals =	$1,092.46		$1,191.9107	$1,191.91	$1,191.90	$1,191.80