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	$52.94	4.670%	$55.4123	$55.41	$55.40	$55.40
Purchase #2	$79.60	3.479%	$82.3693	$82.37	$82.35	$82.40
Purchase #3	$130.59	12.786%	$147.2872	$147.29	$147.30	$147.30
Purchase #4	$183.42	4.318%	$191.3401	$191.34	$191.35	$191.30
Purchase #5	$96.43	10.485%	$106.5407	$106.54	$106.55	$106.50
Purchase #6	$22.79	10.778%	$25.2463	$25.25	$25.25	$25.20
Purchase #7	$149.38	12.143%	$167.5192	$167.52	$167.50	$167.50
7 purchase totals =	$715.15		$775.7151	$775.72	$775.70	$775.60