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	$187.69	12.543%	$211.232	$211.23	$211.25	$211.20
Purchase #2	$170.51	5.489%	$179.8693	$179.87	$179.85	$179.90
Purchase #3	$198.43	5.446%	$209.2365	$209.24	$209.25	$209.20
Purchase #4	$149.32	4.727%	$156.3784	$156.38	$156.40	$156.40
Purchase #5	$9.95	9.625%	$10.9077	$10.91	$10.90	$10.90
Purchase #6	$180.76	3.779%	$187.5909	$187.59	$187.60	$187.60
Purchase #7	$45.33	5.656%	$47.8939	$47.89	$47.90	$47.90
7 purchase totals =	$941.99		$1,003.1087	$1,003.11	$1,003.15	$1,003.10