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	$128.29	10.391%	$141.6206	$141.62	$141.60	$141.60
Purchase #2	$85.82	6.479%	$91.3803	$91.38	$91.40	$91.40
Purchase #3	$195.60	7.206%	$209.6949	$209.69	$209.70	$209.70
Purchase #4	$205.63	8.179%	$222.4485	$222.45	$222.45	$222.40
Purchase #5	$52.25	9.214%	$57.0643	$57.06	$57.05	$57.10
Purchase #6	$162.76	9.793%	$178.6991	$178.70	$178.70	$178.70
Purchase #7	$130.27	13.285%	$147.5764	$147.58	$147.60	$147.60
7 purchase totals =	$960.62		$1,048.4841	$1,048.48	$1,048.50	$1,048.50