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	$233.26	4.294%	$243.2762	$243.28	$243.30	$243.30
Purchase #2	$159.77	4.731%	$167.3287	$167.33	$167.35	$167.30
Purchase #3	$74.78	12.207%	$83.9084	$83.91	$83.90	$83.90
Purchase #4	$158.41	10.735%	$175.4153	$175.42	$175.40	$175.40
Purchase #5	$109.41	12.639%	$123.2383	$123.24	$123.25	$123.20
Purchase #6	$113.89	11.344%	$126.8097	$126.81	$126.80	$126.80
Purchase #7	$185.60	12.269%	$208.3713	$208.37	$208.35	$208.40
7 purchase totals =	$1,035.12		$1,128.3479	$1,128.36	$1,128.35	$1,128.30