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	$218.31	6.219%	$231.8867	$231.89	$231.90	$231.90
Purchase #2	$175.91	9.159%	$192.0216	$192.02	$192.00	$192.00
Purchase #3	$250.82	5.634%	$264.9512	$264.95	$264.95	$265.00
Purchase #4	$89.40	11.205%	$99.4173	$99.42	$99.40	$99.40
Purchase #5	$47.47	11.139%	$52.7577	$52.76	$52.75	$52.80
Purchase #6	$114.97	13.280%	$130.238	$130.24	$130.25	$130.20
Purchase #7	$119.77	3.380%	$123.8182	$123.82	$123.80	$123.80
7 purchase totals =	$1,016.65		$1,095.0907	$1,095.10	$1,095.05	$1,095.10