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	$52.87	3.464%	$54.7014	$54.70	$54.70	$54.70
Purchase #2	$234.74	12.789%	$264.7609	$264.76	$264.75	$264.80
Purchase #3	$59.28	8.111%	$64.0882	$64.09	$64.10	$64.10
Purchase #4	$147.83	12.399%	$166.1594	$166.16	$166.15	$166.20
Purchase #5	$210.88	13.615%	$239.5913	$239.59	$239.60	$239.60
Purchase #6	$75.71	13.273%	$85.759	$85.76	$85.75	$85.80
Purchase #7	$134.96	12.564%	$151.9164	$151.92	$151.90	$151.90
7 purchase totals =	$916.27		$1,026.9766	$1,026.98	$1,026.95	$1,027.10