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	$83.61	7.187%	$89.6191	$89.62	$89.60	$89.60
Purchase #2	$105.92	7.636%	$114.0081	$114.01	$114.00	$114.00
Purchase #3	$218.77	6.585%	$233.176	$233.18	$233.20	$233.20
Purchase #4	$150.44	7.867%	$162.2751	$162.28	$162.30	$162.30
Purchase #5	$125.96	3.738%	$130.6684	$130.67	$130.65	$130.70
Purchase #6	$122.54	3.830%	$127.2333	$127.23	$127.25	$127.20
Purchase #7	$105.37	13.206%	$119.2852	$119.29	$119.30	$119.30
7 purchase totals =	$912.61		$976.2652	$976.28	$976.30	$976.30