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	$223.75	5.498%	$236.0518	$236.05	$236.05	$236.10
Purchase #2	$141.89	13.346%	$160.8266	$160.83	$160.85	$160.80
Purchase #3	$104.36	9.453%	$114.2252	$114.23	$114.25	$114.20
Purchase #4	$106.40	12.383%	$119.5755	$119.58	$119.60	$119.60
Purchase #5	$42.30	3.631%	$43.8359	$43.84	$43.85	$43.80
Purchase #6	$223.89	4.450%	$233.8531	$233.85	$233.85	$233.90
Purchase #7	$170.72	4.479%	$178.3665	$178.37	$178.35	$178.40
7 purchase totals =	$1,013.31		$1,086.7346	$1,086.75	$1,086.80	$1,086.80