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	$48.98	9.834%	$53.7967	$53.80	$53.80	$53.80
Purchase #2	$190.79	12.209%	$214.0836	$214.08	$214.10	$214.10
Purchase #3	$72.83	6.869%	$77.8327	$77.83	$77.85	$77.80
Purchase #4	$225.31	13.802%	$256.4073	$256.41	$256.40	$256.40
Purchase #5	$179.30	3.663%	$185.8678	$185.87	$185.85	$185.90
Purchase #6	$231.25	4.304%	$241.203	$241.20	$241.20	$241.20
Purchase #7	$54.52	12.458%	$61.3121	$61.31	$61.30	$61.30
7 purchase totals =	$1,002.98		$1,090.5032	$1,090.50	$1,090.50	$1,090.50