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	$214.80	7.111%	$230.0744	$230.07	$230.05	$230.10
Purchase #2	$61.78	4.786%	$64.7368	$64.74	$64.75	$64.70
Purchase #3	$162.72	6.826%	$173.8273	$173.83	$173.85	$173.80
Purchase #4	$119.41	3.120%	$123.1356	$123.14	$123.15	$123.10
Purchase #5	$35.63	10.819%	$39.4848	$39.48	$39.50	$39.50
Purchase #6	$245.48	13.160%	$277.7852	$277.79	$277.80	$277.80
Purchase #7	$162.56	5.254%	$171.1009	$171.10	$171.10	$171.10
7 purchase totals =	$1,002.38		$1,080.1450	$1,080.15	$1,080.20	$1,080.10