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	$229.93	6.874%	$245.7354	$245.74	$245.75	$245.70
Purchase #2	$184.66	3.267%	$190.6928	$190.69	$190.70	$190.70
Purchase #3	$91.59	5.751%	$96.8573	$96.86	$96.85	$96.90
Purchase #4	$78.63	8.623%	$85.4103	$85.41	$85.40	$85.40
Purchase #5	$206.40	12.329%	$231.8471	$231.85	$231.85	$231.80
Purchase #6	$94.56	11.442%	$105.3796	$105.38	$105.40	$105.40
Purchase #7	$214.40	7.121%	$229.6674	$229.67	$229.65	$229.70
7 purchase totals =	$1,100.17		$1,185.5899	$1,185.60	$1,185.60	$1,185.60