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	$83.85	3.643%	$86.9047	$86.90	$86.90	$86.90
Purchase #2	$110.87	11.374%	$123.4804	$123.48	$123.50	$123.50
Purchase #3	$64.56	11.752%	$72.1471	$72.15	$72.15	$72.10
Purchase #4	$119.94	13.180%	$135.7481	$135.75	$135.75	$135.70
Purchase #5	$160.74	6.729%	$171.5562	$171.56	$171.55	$171.60
Purchase #6	$185.48	10.589%	$205.1205	$205.12	$205.10	$205.10
Purchase #7	$110.39	4.546%	$115.4083	$115.41	$115.40	$115.40
7 purchase totals =	$835.83		$910.3653	$910.37	$910.35	$910.30