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	$18.41	6.231%	$19.5571	$19.56	$19.55	$19.60
Purchase #2	$23.73	5.179%	$24.959	$24.96	$24.95	$25.00
Purchase #3	$179.43	6.478%	$191.0535	$191.05	$191.05	$191.10
Purchase #4	$31.77	5.861%	$33.632	$33.63	$33.65	$33.60
Purchase #5	$169.96	9.267%	$185.7102	$185.71	$185.70	$185.70
Purchase #6	$40.59	4.717%	$42.5046	$42.50	$42.50	$42.50
Purchase #7	$91.44	4.468%	$95.5255	$95.53	$95.55	$95.50
7 purchase totals =	$555.33		$592.9419	$592.94	$592.95	$593.00