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	$60.73	10.793%	$67.2846	$67.28	$67.30	$67.30
Purchase #2	$172.62	7.365%	$185.3335	$185.33	$185.35	$185.30
Purchase #3	$50.54	7.665%	$54.4139	$54.41	$54.40	$54.40
Purchase #4	$133.30	6.621%	$142.1258	$142.13	$142.15	$142.10
Purchase #5	$149.58	11.855%	$167.3127	$167.31	$167.30	$167.30
Purchase #6	$230.48	4.410%	$240.6442	$240.64	$240.65	$240.60
Purchase #7	$228.86	8.440%	$248.1758	$248.18	$248.20	$248.20
7 purchase totals =	$1,026.11		$1,105.2905	$1,105.28	$1,105.35	$1,105.20