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	$69.64	4.386%	$72.6944	$72.69	$72.70	$72.70
Purchase #2	$117.51	7.131%	$125.8896	$125.89	$125.90	$125.90
Purchase #3	$68.73	11.511%	$76.6415	$76.64	$76.65	$76.60
Purchase #4	$79.36	7.423%	$85.2509	$85.25	$85.25	$85.30
Purchase #5	$116.44	12.206%	$130.6527	$130.65	$130.65	$130.70
Purchase #6	$96.86	6.346%	$103.0067	$103.01	$103.00	$103.00
Purchase #7	$98.83	10.620%	$109.3257	$109.33	$109.35	$109.30
7 purchase totals =	$647.37		$703.4615	$703.46	$703.50	$703.50