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	$11.35	7.383%	$12.188	$12.19	$12.20	$12.20
Purchase #2	$236.63	7.736%	$254.9357	$254.94	$254.95	$254.90
Purchase #3	$116.86	11.504%	$130.3036	$130.30	$130.30	$130.30
Purchase #4	$98.68	13.536%	$112.0373	$112.04	$112.05	$112.00
Purchase #5	$164.41	12.512%	$184.981	$184.98	$185.00	$185.00
Purchase #6	$82.88	9.334%	$90.616	$90.62	$90.60	$90.60
Purchase #7	$80.74	10.706%	$89.384	$89.38	$89.40	$89.40
7 purchase totals =	$791.55		$874.4456	$874.45	$874.50	$874.40