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	$156.40	11.753%	$174.7817	$174.78	$174.80	$174.80
Purchase #2	$71.88	6.874%	$76.821	$76.82	$76.80	$76.80
Purchase #3	$125.31	13.387%	$142.0852	$142.09	$142.10	$142.10
Purchase #4	$211.90	8.538%	$229.992	$229.99	$230.00	$230.00
Purchase #5	$192.80	8.830%	$209.8242	$209.82	$209.80	$209.80
Purchase #6	$118.30	4.313%	$123.4023	$123.40	$123.40	$123.40
Purchase #7	$50.59	11.152%	$56.2318	$56.23	$56.25	$56.20
7 purchase totals =	$927.18		$1,013.1382	$1,013.13	$1,013.15	$1,013.10