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	$49.48	9.503%	$54.1821	$54.18	$54.20	$54.20
Purchase #2	$121.45	5.222%	$127.7921	$127.79	$127.80	$127.80
Purchase #3	$228.33	6.649%	$243.5117	$243.51	$243.50	$243.50
Purchase #4	$249.32	5.631%	$263.3592	$263.36	$263.35	$263.40
Purchase #5	$64.85	13.324%	$73.4906	$73.49	$73.50	$73.50
Purchase #6	$69.56	11.380%	$77.4759	$77.48	$77.50	$77.50
Purchase #7	$211.59	7.120%	$226.6552	$226.66	$226.65	$226.70
7 purchase totals =	$994.58		$1,066.4668	$1,066.47	$1,066.50	$1,066.60