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	$63.65	3.454%	$65.8485	$65.85	$65.85	$65.80
Purchase #2	$44.39	3.353%	$45.8784	$45.88	$45.90	$45.90
Purchase #3	$120.94	5.277%	$127.322	$127.32	$127.30	$127.30
Purchase #4	$229.41	5.633%	$242.3327	$242.33	$242.35	$242.30
Purchase #5	$110.85	13.745%	$126.0863	$126.09	$126.10	$126.10
Purchase #6	$86.56	6.801%	$92.4469	$92.45	$92.45	$92.40
Purchase #7	$240.28	4.287%	$250.5808	$250.58	$250.60	$250.60
7 purchase totals =	$896.08		$950.4956	$950.50	$950.55	$950.40