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	$46.31	3.219%	$47.8007	$47.80	$47.80	$47.80
Purchase #2	$223.83	13.258%	$253.5054	$253.51	$253.50	$253.50
Purchase #3	$103.96	5.327%	$109.4979	$109.50	$109.50	$109.50
Purchase #4	$150.84	10.420%	$166.5575	$166.56	$166.55	$166.60
Purchase #5	$142.98	8.388%	$154.9732	$154.97	$154.95	$155.00
Purchase #6	$171.71	6.163%	$182.2925	$182.29	$182.30	$182.30
Purchase #7	$98.82	4.433%	$103.2007	$103.20	$103.20	$103.20
7 purchase totals =	$938.45		$1,017.8279	$1,017.83	$1,017.80	$1,017.90