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	$108.26	9.104%	$118.116	$118.12	$118.10	$118.10
Purchase #2	$167.28	11.410%	$186.3666	$186.37	$186.35	$186.40
Purchase #3	$77.44	12.213%	$86.8977	$86.90	$86.90	$86.90
Purchase #4	$164.69	4.308%	$171.7848	$171.78	$171.80	$171.80
Purchase #5	$82.79	12.206%	$92.8953	$92.90	$92.90	$92.90
Purchase #6	$245.87	11.432%	$273.9779	$273.98	$274.00	$274.00
Purchase #7	$142.29	6.180%	$151.0835	$151.08	$151.10	$151.10
7 purchase totals =	$988.62		$1,081.1218	$1,081.13	$1,081.15	$1,081.20