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	$43.29	6.407%	$46.0636	$46.06	$46.05	$46.10
Purchase #2	$178.72	3.669%	$185.2772	$185.28	$185.30	$185.30
Purchase #3	$216.56	9.847%	$237.8847	$237.88	$237.90	$237.90
Purchase #4	$240.38	13.367%	$272.5116	$272.51	$272.50	$272.50
Purchase #5	$196.72	4.758%	$206.0799	$206.08	$206.10	$206.10
Purchase #6	$55.59	3.689%	$57.6407	$57.64	$57.65	$57.60
Purchase #7	$169.29	11.512%	$188.7787	$188.78	$188.80	$188.80
7 purchase totals =	$1,100.55		$1,194.2364	$1,194.23	$1,194.30	$1,194.30