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	$133.75	6.370%	$142.2699	$142.27	$142.25	$142.30
Purchase #2	$49.41	13.224%	$55.944	$55.94	$55.95	$55.90
Purchase #3	$170.92	11.334%	$190.2921	$190.29	$190.30	$190.30
Purchase #4	$90.34	6.352%	$96.0784	$96.08	$96.10	$96.10
Purchase #5	$117.87	7.374%	$126.5617	$126.56	$126.55	$126.60
Purchase #6	$11.33	4.423%	$11.8311	$11.83	$11.85	$11.80
Purchase #7	$183.84	4.771%	$192.611	$192.61	$192.60	$192.60
7 purchase totals =	$757.46		$815.5882	$815.58	$815.60	$815.60