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	$30.82	6.411%	$32.7959	$32.80	$32.80	$32.80
Purchase #2	$47.33	12.565%	$53.277	$53.28	$53.30	$53.30
Purchase #3	$27.77	12.695%	$31.2954	$31.30	$31.30	$31.30
Purchase #4	$35.53	11.132%	$39.4852	$39.49	$39.50	$39.50
Purchase #5	$26.61	4.523%	$27.8136	$27.81	$27.80	$27.80
Purchase #6	$35.69	11.681%	$39.8589	$39.86	$39.85	$39.90
Purchase #7	$36.86	5.567%	$38.912	$38.91	$38.90	$38.90
7 purchase totals =	$240.61		$263.4380	$263.45	$263.45	$263.50