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	$224.44	8.349%	$243.1785	$243.18	$243.20	$243.20
Purchase #2	$101.76	4.478%	$106.3168	$106.32	$106.30	$106.30
Purchase #3	$90.33	6.409%	$96.1192	$96.12	$96.10	$96.10
Purchase #4	$192.85	11.859%	$215.7201	$215.72	$215.70	$215.70
Purchase #5	$151.91	8.314%	$164.5398	$164.54	$164.55	$164.50
Purchase #6	$117.82	4.640%	$123.2868	$123.29	$123.30	$123.30
Purchase #7	$104.27	3.647%	$108.0727	$108.07	$108.05	$108.10
7 purchase totals =	$983.38		$1,057.2339	$1,057.24	$1,057.20	$1,057.20