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	$91.49	10.324%	$100.9354	$100.94	$100.95	$100.90
Purchase #2	$163.47	12.860%	$184.4922	$184.49	$184.50	$184.50
Purchase #3	$88.77	7.152%	$95.1188	$95.12	$95.10	$95.10
Purchase #4	$59.27	5.503%	$62.5316	$62.53	$62.55	$62.50
Purchase #5	$115.34	12.670%	$129.9536	$129.95	$129.95	$130.00
Purchase #6	$234.87	12.570%	$264.3932	$264.39	$264.40	$264.40
Purchase #7	$156.61	7.183%	$167.8593	$167.86	$167.85	$167.90
7 purchase totals =	$909.82		$1,005.2841	$1,005.28	$1,005.30	$1,005.30