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	$11.36	7.546%	$12.2172	$12.22	$12.20	$12.20
Purchase #2	$31.28	3.770%	$32.4593	$32.46	$32.45	$32.50
Purchase #3	$117.73	8.418%	$127.6405	$127.64	$127.65	$127.60
Purchase #4	$70.35	3.676%	$72.9361	$72.94	$72.95	$72.90
Purchase #5	$194.59	12.707%	$219.3166	$219.32	$219.30	$219.30
Purchase #6	$7.33	5.830%	$7.7573	$7.76	$7.75	$7.80
Purchase #7	$217.62	7.694%	$234.3637	$234.36	$234.35	$234.40
7 purchase totals =	$650.26		$706.6907	$706.70	$706.65	$706.70