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	$96.29	13.427%	$109.2189	$109.22	$109.20	$109.20
Purchase #2	$210.37	9.492%	$230.3383	$230.34	$230.35	$230.30
Purchase #3	$80.66	13.512%	$91.5588	$91.56	$91.55	$91.60
Purchase #4	$27.42	13.717%	$31.1812	$31.18	$31.20	$31.20
Purchase #5	$100.32	5.227%	$105.5637	$105.56	$105.55	$105.60
Purchase #6	$119.81	4.435%	$125.1236	$125.12	$125.10	$125.10
Purchase #7	$85.59	4.186%	$89.1728	$89.17	$89.15	$89.20
7 purchase totals =	$720.46		$782.1573	$782.15	$782.10	$782.20