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	$105.44	3.809%	$109.4562	$109.46	$109.45	$109.50
Purchase #2	$170.64	13.629%	$193.8965	$193.90	$193.90	$193.90
Purchase #3	$65.29	9.768%	$71.6675	$71.67	$71.65	$71.70
Purchase #4	$128.36	6.136%	$136.2362	$136.24	$136.25	$136.20
Purchase #5	$187.81	4.516%	$196.2915	$196.29	$196.30	$196.30
Purchase #6	$159.85	6.325%	$169.9605	$169.96	$169.95	$170.00
Purchase #7	$109.26	10.139%	$120.3379	$120.34	$120.35	$120.30
7 purchase totals =	$926.65		$997.8463	$997.86	$997.85	$997.90