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	$72.86	7.729%	$78.4913	$78.49	$78.50	$78.50
Purchase #2	$248.52	13.325%	$281.6353	$281.64	$281.65	$281.60
Purchase #3	$157.41	13.334%	$178.399	$178.40	$178.40	$178.40
Purchase #4	$75.61	13.538%	$85.8461	$85.85	$85.85	$85.80
Purchase #5	$241.47	10.687%	$267.2759	$267.28	$267.30	$267.30
Purchase #6	$218.56	11.572%	$243.8518	$243.85	$243.85	$243.90
Purchase #7	$89.91	7.417%	$96.5786	$96.58	$96.60	$96.60
7 purchase totals =	$1,104.34		$1,232.0780	$1,232.09	$1,232.15	$1,232.10