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	$175.38	3.296%	$181.1605	$181.16	$181.15	$181.20
Purchase #2	$18.83	7.816%	$20.3018	$20.30	$20.30	$20.30
Purchase #3	$175.40	4.445%	$183.1965	$183.20	$183.20	$183.20
Purchase #4	$97.53	12.578%	$109.7973	$109.80	$109.80	$109.80
Purchase #5	$57.27	3.493%	$59.2704	$59.27	$59.25	$59.30
Purchase #6	$98.82	11.836%	$110.5163	$110.52	$110.50	$110.50
Purchase #7	$27.71	8.123%	$29.9609	$29.96	$29.95	$30.00
7 purchase totals =	$650.94		$694.2037	$694.21	$694.15	$694.30