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	$234.27	6.872%	$250.369	$250.37	$250.35	$250.40
Purchase #2	$41.72	10.498%	$46.0998	$46.10	$46.10	$46.10
Purchase #3	$224.70	7.385%	$241.2941	$241.29	$241.30	$241.30
Purchase #4	$92.89	5.502%	$98.0008	$98.00	$98.00	$98.00
Purchase #5	$245.97	4.280%	$256.4975	$256.50	$256.50	$256.50
Purchase #6	$189.56	4.739%	$198.5432	$198.54	$198.55	$198.50
Purchase #7	$149.59	6.703%	$159.617	$159.62	$159.60	$159.60
7 purchase totals =	$1,178.70		$1,250.4214	$1,250.42	$1,250.40	$1,250.40