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	$52.97	12.845%	$59.774	$59.77	$59.75	$59.80
Purchase #2	$228.42	7.375%	$245.266	$245.27	$245.25	$245.30
Purchase #3	$14.86	13.453%	$16.8591	$16.86	$16.85	$16.90
Purchase #4	$70.25	9.506%	$76.928	$76.93	$76.95	$76.90
Purchase #5	$145.96	8.820%	$158.8337	$158.83	$158.85	$158.80
Purchase #6	$213.54	9.254%	$233.301	$233.30	$233.30	$233.30
Purchase #7	$198.69	6.871%	$212.342	$212.34	$212.35	$212.30
7 purchase totals =	$924.69		$1,003.3038	$1,003.30	$1,003.30	$1,003.30