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	$187.43	11.789%	$209.5261	$209.53	$209.55	$209.50
Purchase #2	$209.74	3.623%	$217.3389	$217.34	$217.35	$217.30
Purchase #3	$91.62	13.171%	$103.6873	$103.69	$103.70	$103.70
Purchase #4	$90.47	8.401%	$98.0704	$98.07	$98.05	$98.10
Purchase #5	$52.60	13.514%	$59.7084	$59.71	$59.70	$59.70
Purchase #6	$244.65	8.347%	$265.0709	$265.07	$265.05	$265.10
Purchase #7	$91.39	7.130%	$97.9061	$97.91	$97.90	$97.90
7 purchase totals =	$967.90		$1,051.3081	$1,051.32	$1,051.30	$1,051.30