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	$93.48	6.473%	$99.531	$99.53	$99.55	$99.50
Purchase #2	$231.55	13.611%	$263.0663	$263.07	$263.05	$263.10
Purchase #3	$209.65	11.121%	$232.9652	$232.97	$232.95	$233.00
Purchase #4	$29.78	10.396%	$32.8759	$32.88	$32.90	$32.90
Purchase #5	$54.65	13.721%	$62.1485	$62.15	$62.15	$62.10
Purchase #6	$56.40	5.656%	$59.59	$59.59	$59.60	$59.60
Purchase #7	$93.89	4.533%	$98.146	$98.15	$98.15	$98.10
7 purchase totals =	$769.40		$848.3229	$848.34	$848.35	$848.30