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	$146.86	6.358%	$156.1974	$156.20	$156.20	$156.20
Purchase #2	$173.54	6.745%	$185.2453	$185.25	$185.25	$185.20
Purchase #3	$240.52	4.304%	$250.872	$250.87	$250.85	$250.90
Purchase #4	$97.97	7.627%	$105.4422	$105.44	$105.45	$105.40
Purchase #5	$141.53	13.652%	$160.8517	$160.85	$160.85	$160.90
Purchase #6	$210.60	6.298%	$223.8636	$223.86	$223.85	$223.90
Purchase #7	$209.28	6.748%	$223.4022	$223.40	$223.40	$223.40
7 purchase totals =	$1,220.30		$1,305.8744	$1,305.87	$1,305.85	$1,305.90