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	$90.62	5.825%	$95.8986	$95.90	$95.90	$95.90
Purchase #2	$26.98	6.477%	$28.7275	$28.73	$28.75	$28.70
Purchase #3	$6.88	9.213%	$7.5139	$7.51	$7.50	$7.50
Purchase #4	$32.36	3.345%	$33.4424	$33.44	$33.45	$33.40
Purchase #5	$64.91	3.751%	$67.3448	$67.34	$67.35	$67.30
Purchase #6	$17.93	11.664%	$20.0214	$20.02	$20.00	$20.00
Purchase #7	$179.36	11.511%	$200.0061	$200.01	$200.00	$200.00
7 purchase totals =	$419.04		$452.9547	$452.95	$452.95	$452.80