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	$180.49	11.707%	$201.62	$201.62	$201.60	$201.60
Purchase #2	$10.38	10.241%	$11.443	$11.44	$11.45	$11.40
Purchase #3	$147.33	10.600%	$162.947	$162.95	$162.95	$162.90
Purchase #4	$96.45	12.612%	$108.6143	$108.61	$108.60	$108.60
Purchase #5	$146.88	10.496%	$162.2965	$162.30	$162.30	$162.30
Purchase #6	$98.67	5.230%	$103.8304	$103.83	$103.85	$103.80
Purchase #7	$159.52	5.418%	$168.1628	$168.16	$168.15	$168.20
7 purchase totals =	$839.72		$918.9140	$918.91	$918.90	$918.80