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	$79.92	6.759%	$85.3218	$85.32	$85.30	$85.30
Purchase #2	$23.52	4.639%	$24.6111	$24.61	$24.60	$24.60
Purchase #3	$167.41	6.445%	$178.1996	$178.20	$178.20	$178.20
Purchase #4	$229.90	10.747%	$254.6074	$254.61	$254.60	$254.60
Purchase #5	$127.33	10.792%	$141.0715	$141.07	$141.05	$141.10
Purchase #6	$231.39	6.190%	$245.713	$245.71	$245.70	$245.70
Purchase #7	$142.54	5.219%	$149.9792	$149.98	$150.00	$150.00
7 purchase totals =	$1,002.01		$1,079.5036	$1,079.50	$1,079.45	$1,079.50