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	$54.30	5.245%	$57.148	$57.15	$57.15	$57.10
Purchase #2	$99.57	10.834%	$110.3574	$110.36	$110.35	$110.40
Purchase #3	$84.34	7.418%	$90.5963	$90.60	$90.60	$90.60
Purchase #4	$124.50	4.392%	$129.968	$129.97	$129.95	$130.00
Purchase #5	$223.88	6.464%	$238.3516	$238.35	$238.35	$238.40
Purchase #6	$219.98	4.714%	$230.3499	$230.35	$230.35	$230.30
Purchase #7	$39.38	11.375%	$43.8595	$43.86	$43.85	$43.90
7 purchase totals =	$845.95		$900.6307	$900.64	$900.60	$900.70