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	$96.75	8.496%	$104.9699	$104.97	$104.95	$105.00
Purchase #2	$200.27	12.432%	$225.1676	$225.17	$225.15	$225.20
Purchase #3	$151.61	6.557%	$161.5511	$161.55	$161.55	$161.60
Purchase #4	$50.76	4.197%	$52.8904	$52.89	$52.90	$52.90
Purchase #5	$142.58	3.525%	$147.6059	$147.61	$147.60	$147.60
Purchase #6	$238.76	6.693%	$254.7402	$254.74	$254.75	$254.70
Purchase #7	$238.62	4.520%	$249.4056	$249.41	$249.40	$249.40
7 purchase totals =	$1,119.35		$1,196.3307	$1,196.34	$1,196.30	$1,196.40