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	$243.69	8.543%	$264.5084	$264.51	$264.50	$264.50
Purchase #2	$149.41	8.867%	$162.6582	$162.66	$162.65	$162.70
Purchase #3	$242.44	6.544%	$258.3053	$258.31	$258.30	$258.30
Purchase #4	$192.36	12.592%	$216.582	$216.58	$216.60	$216.60
Purchase #5	$159.66	8.571%	$173.3445	$173.34	$173.35	$173.30
Purchase #6	$178.49	10.269%	$196.8191	$196.82	$196.80	$196.80
Purchase #7	$94.69	11.587%	$105.6617	$105.66	$105.65	$105.70
7 purchase totals =	$1,260.74		$1,377.8792	$1,377.88	$1,377.85	$1,377.90