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	$154.30	4.708%	$161.5644	$161.56	$161.55	$161.60
Purchase #2	$234.73	5.792%	$248.3256	$248.33	$248.35	$248.30
Purchase #3	$233.91	4.778%	$245.0862	$245.09	$245.10	$245.10
Purchase #4	$45.25	9.384%	$49.4963	$49.50	$49.50	$49.50
Purchase #5	$37.57	6.473%	$40.0019	$40.00	$40.00	$40.00
Purchase #6	$171.55	13.432%	$194.5926	$194.59	$194.60	$194.60
Purchase #7	$143.67	6.428%	$152.9051	$152.91	$152.90	$152.90
7 purchase totals =	$1,020.98		$1,091.9721	$1,091.98	$1,092.00	$1,092.00