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	$43.39	4.673%	$45.4176	$45.42	$45.40	$45.40
Purchase #2	$81.44	11.240%	$90.5939	$90.59	$90.60	$90.60
Purchase #3	$5.71	12.288%	$6.4116	$6.41	$6.40	$6.40
Purchase #4	$67.97	4.582%	$71.0844	$71.08	$71.10	$71.10
Purchase #5	$89.38	5.655%	$94.4344	$94.43	$94.45	$94.40
Purchase #6	$99.37	12.148%	$111.4415	$111.44	$111.45	$111.40
Purchase #7	$39.91	7.248%	$42.8027	$42.80	$42.80	$42.80
7 purchase totals =	$427.17		$462.1861	$462.17	$462.20	$462.10