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	$150.61	13.104%	$170.3459	$170.35	$170.35	$170.30
Purchase #2	$215.69	6.223%	$229.1124	$229.11	$229.10	$229.10
Purchase #3	$55.93	9.217%	$61.0851	$61.09	$61.10	$61.10
Purchase #4	$145.51	11.697%	$162.5303	$162.53	$162.55	$162.50
Purchase #5	$118.60	4.428%	$123.8516	$123.85	$123.85	$123.90
Purchase #6	$236.37	3.147%	$243.8086	$243.81	$243.80	$243.80
Purchase #7	$158.49	12.566%	$178.4059	$178.41	$178.40	$178.40
7 purchase totals =	$1,081.20		$1,169.1398	$1,169.15	$1,169.15	$1,169.10