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	$166.77	11.430%	$185.8318	$185.83	$185.85	$185.80
Purchase #2	$156.43	7.599%	$168.3171	$168.32	$168.30	$168.30
Purchase #3	$82.36	4.236%	$85.8488	$85.85	$85.85	$85.80
Purchase #4	$150.71	6.872%	$161.0668	$161.07	$161.05	$161.10
Purchase #5	$173.72	10.133%	$191.323	$191.32	$191.30	$191.30
Purchase #6	$95.62	4.177%	$99.614	$99.61	$99.60	$99.60
Purchase #7	$120.69	8.449%	$130.8871	$130.89	$130.90	$130.90
7 purchase totals =	$946.30		$1,022.8886	$1,022.89	$1,022.85	$1,022.80