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	$183.79	7.764%	$198.0595	$198.06	$198.05	$198.10
Purchase #2	$242.31	9.621%	$265.6226	$265.62	$265.60	$265.60
Purchase #3	$129.46	12.297%	$145.3797	$145.38	$145.40	$145.40
Purchase #4	$109.64	12.623%	$123.4799	$123.48	$123.50	$123.50
Purchase #5	$24.44	13.211%	$27.6688	$27.67	$27.65	$27.70
Purchase #6	$81.64	8.487%	$88.5688	$88.57	$88.55	$88.60
Purchase #7	$230.72	7.560%	$248.1624	$248.16	$248.15	$248.20
7 purchase totals =	$1,002.00		$1,096.9417	$1,096.94	$1,096.90	$1,097.10