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	$85.89	12.280%	$96.4373	$96.44	$96.45	$96.40
Purchase #2	$240.56	12.629%	$270.9403	$270.94	$270.95	$270.90
Purchase #3	$167.73	3.439%	$173.4982	$173.50	$173.50	$173.50
Purchase #4	$106.60	9.594%	$116.8272	$116.83	$116.85	$116.80
Purchase #5	$54.71	10.272%	$60.3298	$60.33	$60.35	$60.30
Purchase #6	$166.68	9.404%	$182.3546	$182.35	$182.35	$182.40
Purchase #7	$91.28	10.667%	$101.0168	$101.02	$101.00	$101.00
7 purchase totals =	$913.45		$1,001.4042	$1,001.41	$1,001.45	$1,001.30