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	$198.66	8.420%	$215.3872	$215.39	$215.40	$215.40
Purchase #2	$246.74	12.736%	$278.1648	$278.16	$278.15	$278.20
Purchase #3	$203.27	12.773%	$229.2337	$229.23	$229.25	$229.20
Purchase #4	$222.44	4.418%	$232.2674	$232.27	$232.25	$232.30
Purchase #5	$35.96	6.745%	$38.3855	$38.39	$38.40	$38.40
Purchase #6	$47.26	6.115%	$50.1499	$50.15	$50.15	$50.10
Purchase #7	$62.63	7.661%	$67.4281	$67.43	$67.45	$67.40
7 purchase totals =	$1,016.96		$1,111.0166	$1,111.02	$1,111.05	$1,111.00