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	$81.69	4.540%	$85.3987	$85.40	$85.40	$85.40
Purchase #2	$151.99	4.302%	$158.5286	$158.53	$158.55	$158.50
Purchase #3	$65.88	7.474%	$70.8039	$70.80	$70.80	$70.80
Purchase #4	$126.81	12.612%	$142.8033	$142.80	$142.80	$142.80
Purchase #5	$249.57	5.851%	$264.1723	$264.17	$264.15	$264.20
Purchase #6	$249.89	7.308%	$268.152	$268.15	$268.15	$268.20
Purchase #7	$168.32	4.483%	$175.8658	$175.87	$175.85	$175.90
7 purchase totals =	$1,094.15		$1,165.7246	$1,165.72	$1,165.70	$1,165.80