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	$196.42	12.654%	$221.275	$221.28	$221.30	$221.30
Purchase #2	$104.66	5.813%	$110.7439	$110.74	$110.75	$110.70
Purchase #3	$5.81	11.253%	$6.4638	$6.46	$6.45	$6.50
Purchase #4	$233.62	6.626%	$249.0997	$249.10	$249.10	$249.10
Purchase #5	$92.93	6.562%	$99.0281	$99.03	$99.05	$99.00
Purchase #6	$82.83	8.197%	$89.6196	$89.62	$89.60	$89.60
Purchase #7	$215.81	11.315%	$240.2289	$240.23	$240.25	$240.20
7 purchase totals =	$932.08		$1,016.4590	$1,016.46	$1,016.50	$1,016.40