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	$150.65	9.602%	$165.1154	$165.12	$165.10	$165.10
Purchase #2	$17.94	10.824%	$19.8818	$19.88	$19.90	$19.90
Purchase #3	$89.58	10.854%	$99.303	$99.30	$99.30	$99.30
Purchase #4	$31.61	3.664%	$32.7682	$32.77	$32.75	$32.80
Purchase #5	$84.94	10.224%	$93.6243	$93.62	$93.60	$93.60
Purchase #6	$72.52	13.711%	$82.4632	$82.46	$82.45	$82.50
Purchase #7	$64.56	6.397%	$68.6899	$68.69	$68.70	$68.70
7 purchase totals =	$511.80		$561.8458	$561.84	$561.80	$561.90