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	$163.80	6.568%	$174.5584	$174.56	$174.55	$174.60
Purchase #2	$155.48	9.695%	$170.5538	$170.55	$170.55	$170.60
Purchase #3	$137.82	13.781%	$156.813	$156.81	$156.80	$156.80
Purchase #4	$129.39	12.834%	$145.9959	$146.00	$146.00	$146.00
Purchase #5	$91.80	9.352%	$100.3851	$100.39	$100.40	$100.40
Purchase #6	$39.66	13.452%	$44.9951	$45.00	$45.00	$45.00
Purchase #7	$200.72	13.829%	$228.4776	$228.48	$228.50	$228.50
7 purchase totals =	$918.67		$1,021.7789	$1,021.79	$1,021.80	$1,021.90