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	$187.71	8.830%	$204.2848	$204.28	$204.30	$204.30
Purchase #2	$244.65	4.386%	$255.3803	$255.38	$255.40	$255.40
Purchase #3	$146.97	11.643%	$164.0817	$164.08	$164.10	$164.10
Purchase #4	$63.42	3.731%	$65.7862	$65.79	$65.80	$65.80
Purchase #5	$92.83	3.732%	$96.2944	$96.29	$96.30	$96.30
Purchase #6	$133.64	10.281%	$147.3795	$147.38	$147.40	$147.40
Purchase #7	$248.32	3.200%	$256.2662	$256.27	$256.25	$256.30
7 purchase totals =	$1,117.54		$1,189.4731	$1,189.47	$1,189.55	$1,189.60