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	$80.30	9.666%	$88.0618	$88.06	$88.05	$88.10
Purchase #2	$171.87	5.770%	$181.7869	$181.79	$181.80	$181.80
Purchase #3	$25.42	10.643%	$28.1255	$28.13	$28.15	$28.10
Purchase #4	$203.98	9.397%	$223.148	$223.15	$223.15	$223.10
Purchase #5	$197.82	13.184%	$223.9006	$223.90	$223.90	$223.90
Purchase #6	$157.89	12.139%	$177.0563	$177.06	$177.05	$177.10
Purchase #7	$114.87	7.529%	$123.5186	$123.52	$123.50	$123.50
7 purchase totals =	$952.15		$1,045.5977	$1,045.61	$1,045.60	$1,045.60