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	$149.76	12.165%	$167.9783	$167.98	$168.00	$168.00
Purchase #2	$168.40	7.554%	$181.1209	$181.12	$181.10	$181.10
Purchase #3	$28.92	12.816%	$32.6264	$32.63	$32.65	$32.60
Purchase #4	$153.34	10.377%	$169.2521	$169.25	$169.25	$169.30
Purchase #5	$104.72	11.114%	$116.3586	$116.36	$116.35	$116.40
Purchase #6	$227.65	12.355%	$255.7762	$255.78	$255.80	$255.80
Purchase #7	$45.85	11.195%	$50.9829	$50.98	$51.00	$51.00
7 purchase totals =	$878.64		$974.0954	$974.10	$974.15	$974.20