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	$139.93	4.268%	$145.9022	$145.90	$145.90	$145.90
Purchase #2	$184.37	6.407%	$196.1826	$196.18	$196.20	$196.20
Purchase #3	$197.35	10.623%	$218.3145	$218.31	$218.30	$218.30
Purchase #4	$241.75	8.119%	$261.3777	$261.38	$261.40	$261.40
Purchase #5	$173.92	5.177%	$182.9238	$182.92	$182.90	$182.90
Purchase #6	$150.56	11.655%	$168.1078	$168.11	$168.10	$168.10
Purchase #7	$88.59	7.612%	$95.3335	$95.33	$95.35	$95.30
7 purchase totals =	$1,176.47		$1,268.1421	$1,268.13	$1,268.15	$1,268.10