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	$171.78	7.791%	$185.1634	$185.16	$185.15	$185.20
Purchase #2	$46.80	4.857%	$49.0731	$49.07	$49.05	$49.10
Purchase #3	$35.33	5.253%	$37.1859	$37.19	$37.20	$37.20
Purchase #4	$242.33	4.558%	$253.3754	$253.38	$253.40	$253.40
Purchase #5	$232.66	4.494%	$243.1157	$243.12	$243.10	$243.10
Purchase #6	$210.72	13.117%	$238.3601	$238.36	$238.35	$238.40
Purchase #7	$95.62	10.571%	$105.728	$105.73	$105.75	$105.70
7 purchase totals =	$1,035.24		$1,112.0016	$1,112.01	$1,112.00	$1,112.10