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	$123.33	5.825%	$130.514	$130.51	$130.50	$130.50
Purchase #2	$167.32	11.407%	$186.4062	$186.41	$186.40	$186.40
Purchase #3	$118.73	12.483%	$133.5511	$133.55	$133.55	$133.60
Purchase #4	$153.41	13.707%	$174.4379	$174.44	$174.45	$174.40
Purchase #5	$163.57	10.530%	$180.7939	$180.79	$180.80	$180.80
Purchase #6	$136.63	10.141%	$150.4856	$150.49	$150.50	$150.50
Purchase #7	$123.71	6.588%	$131.86	$131.86	$131.85	$131.90
7 purchase totals =	$986.70		$1,088.0487	$1,088.05	$1,088.05	$1,088.10