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	$55.82	12.825%	$62.9789	$62.98	$63.00	$63.00
Purchase #2	$25.89	11.842%	$28.9559	$28.96	$28.95	$29.00
Purchase #3	$238.57	10.309%	$263.1642	$263.16	$263.15	$263.20
Purchase #4	$237.47	11.464%	$264.6936	$264.69	$264.70	$264.70
Purchase #5	$154.99	6.818%	$165.5572	$165.56	$165.55	$165.60
Purchase #6	$80.41	12.656%	$90.5867	$90.59	$90.60	$90.60
Purchase #7	$162.65	6.549%	$173.3019	$173.30	$173.30	$173.30
7 purchase totals =	$955.80		$1,049.2384	$1,049.24	$1,049.25	$1,049.40