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	$190.89	6.672%	$203.6262	$203.63	$203.65	$203.60
Purchase #2	$219.83	13.869%	$250.3182	$250.32	$250.30	$250.30
Purchase #3	$79.49	8.445%	$86.2029	$86.20	$86.20	$86.20
Purchase #4	$76.43	4.804%	$80.1017	$80.10	$80.10	$80.10
Purchase #5	$180.28	6.397%	$191.8125	$191.81	$191.80	$191.80
Purchase #6	$165.76	4.642%	$173.4546	$173.45	$173.45	$173.50
Purchase #7	$86.90	4.832%	$91.099	$91.10	$91.10	$91.10
7 purchase totals =	$999.58		$1,076.6151	$1,076.61	$1,076.60	$1,076.60