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	$213.77	4.214%	$222.7783	$222.78	$222.80	$222.80
Purchase #2	$73.41	12.210%	$82.3734	$82.37	$82.35	$82.40
Purchase #3	$26.78	7.669%	$28.8338	$28.83	$28.85	$28.80
Purchase #4	$206.90	7.349%	$222.1051	$222.11	$222.10	$222.10
Purchase #5	$131.62	8.194%	$142.4049	$142.40	$142.40	$142.40
Purchase #6	$67.28	12.394%	$75.6187	$75.62	$75.60	$75.60
Purchase #7	$171.61	5.755%	$181.4862	$181.49	$181.50	$181.50
7 purchase totals =	$891.37		$955.6004	$955.60	$955.60	$955.60