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	$55.52	7.709%	$59.8	$59.80	$59.80	$59.80
Purchase #2	$21.61	4.280%	$22.5349	$22.53	$22.55	$22.50
Purchase #3	$145.93	4.229%	$152.1014	$152.10	$152.10	$152.10
Purchase #4	$178.80	3.447%	$184.9632	$184.96	$184.95	$185.00
Purchase #5	$27.54	3.102%	$28.3943	$28.39	$28.40	$28.40
Purchase #6	$127.85	4.842%	$134.0405	$134.04	$134.05	$134.00
Purchase #7	$62.70	8.290%	$67.8978	$67.90	$67.90	$67.90
7 purchase totals =	$619.95		$649.7321	$649.72	$649.75	$649.70