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	$213.91	13.786%	$243.3996	$243.40	$243.40	$243.40
Purchase #2	$250.63	4.810%	$262.6853	$262.69	$262.70	$262.70
Purchase #3	$222.54	6.764%	$237.5926	$237.59	$237.60	$237.60
Purchase #4	$90.38	9.670%	$99.1197	$99.12	$99.10	$99.10
Purchase #5	$166.31	10.302%	$183.4433	$183.44	$183.45	$183.40
Purchase #6	$185.27	10.606%	$204.9197	$204.92	$204.90	$204.90
Purchase #7	$27.39	4.158%	$28.5289	$28.53	$28.55	$28.50
7 purchase totals =	$1,156.43		$1,259.6891	$1,259.69	$1,259.70	$1,259.60