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	$220.58	5.214%	$232.081	$232.08	$232.10	$232.10
Purchase #2	$94.26	9.473%	$103.1892	$103.19	$103.20	$103.20
Purchase #3	$78.73	9.122%	$85.9118	$85.91	$85.90	$85.90
Purchase #4	$33.62	12.117%	$37.6937	$37.69	$37.70	$37.70
Purchase #5	$90.91	8.138%	$98.3083	$98.31	$98.30	$98.30
Purchase #6	$165.45	11.769%	$184.9218	$184.92	$184.90	$184.90
Purchase #7	$244.25	6.561%	$260.2752	$260.28	$260.30	$260.30
7 purchase totals =	$927.80		$1,002.3810	$1,002.38	$1,002.40	$1,002.40