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	$169.33	12.114%	$189.8426	$189.84	$189.85	$189.80
Purchase #2	$153.31	7.551%	$164.8864	$164.89	$164.90	$164.90
Purchase #3	$109.56	5.737%	$115.8455	$115.85	$115.85	$115.80
Purchase #4	$179.92	11.648%	$200.8771	$200.88	$200.90	$200.90
Purchase #5	$61.60	7.629%	$66.2995	$66.30	$66.30	$66.30
Purchase #6	$165.98	3.377%	$171.5851	$171.59	$171.60	$171.60
Purchase #7	$104.61	8.590%	$113.596	$113.60	$113.60	$113.60
7 purchase totals =	$944.31		$1,022.9322	$1,022.95	$1,023.00	$1,022.90