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	$167.25	4.109%	$174.1223	$174.12	$174.10	$174.10
Purchase #2	$84.73	3.455%	$87.6574	$87.66	$87.65	$87.70
Purchase #3	$56.35	5.774%	$59.6036	$59.60	$59.60	$59.60
Purchase #4	$102.41	8.525%	$111.1405	$111.14	$111.15	$111.10
Purchase #5	$110.80	5.306%	$116.679	$116.68	$116.70	$116.70
Purchase #6	$127.47	3.254%	$131.6179	$131.62	$131.60	$131.60
Purchase #7	$65.33	4.693%	$68.3959	$68.40	$68.40	$68.40
7 purchase totals =	$714.34		$749.2166	$749.22	$749.20	$749.20