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	$242.76	8.356%	$263.045	$263.05	$263.05	$263.00
Purchase #2	$223.62	7.285%	$239.9107	$239.91	$239.90	$239.90
Purchase #3	$30.63	4.290%	$31.944	$31.94	$31.95	$31.90
Purchase #4	$110.33	11.523%	$123.0433	$123.04	$123.05	$123.00
Purchase #5	$205.91	13.237%	$233.1663	$233.17	$233.15	$233.20
Purchase #6	$91.84	10.307%	$101.3059	$101.31	$101.30	$101.30
Purchase #7	$245.29	7.841%	$264.5232	$264.52	$264.50	$264.50
7 purchase totals =	$1,150.38		$1,256.9384	$1,256.94	$1,256.90	$1,256.80