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	$167.59	11.405%	$186.7036	$186.70	$186.70	$186.70
Purchase #2	$146.59	12.517%	$164.9387	$164.94	$164.95	$164.90
Purchase #3	$174.36	12.673%	$196.4566	$196.46	$196.45	$196.50
Purchase #4	$211.28	11.547%	$235.6765	$235.68	$235.70	$235.70
Purchase #5	$93.98	12.113%	$105.3638	$105.36	$105.35	$105.40
Purchase #6	$89.76	10.196%	$98.9119	$98.91	$98.90	$98.90
Purchase #7	$92.44	11.678%	$103.2351	$103.24	$103.25	$103.20
7 purchase totals =	$976.00		$1,091.2862	$1,091.29	$1,091.30	$1,091.30