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	$82.44	8.414%	$89.3765	$89.38	$89.40	$89.40
Purchase #2	$189.48	7.392%	$203.4864	$203.49	$203.50	$203.50
Purchase #3	$55.31	13.672%	$62.872	$62.87	$62.85	$62.90
Purchase #4	$156.98	6.852%	$167.7363	$167.74	$167.75	$167.70
Purchase #5	$128.80	5.464%	$135.8376	$135.84	$135.85	$135.80
Purchase #6	$230.82	3.445%	$238.7717	$238.77	$238.75	$238.80
Purchase #7	$109.46	7.864%	$118.0679	$118.07	$118.05	$118.10
7 purchase totals =	$953.29		$1,016.1484	$1,016.16	$1,016.15	$1,016.20