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	$150.30	9.651%	$164.8055	$164.81	$164.80	$164.80
Purchase #2	$67.40	5.745%	$71.2721	$71.27	$71.25	$71.30
Purchase #3	$71.98	10.332%	$79.417	$79.42	$79.40	$79.40
Purchase #4	$219.56	10.173%	$241.8958	$241.90	$241.90	$241.90
Purchase #5	$179.30	3.411%	$185.4159	$185.42	$185.40	$185.40
Purchase #6	$139.34	13.839%	$158.6233	$158.62	$158.60	$158.60
Purchase #7	$98.32	13.302%	$111.3985	$111.40	$111.40	$111.40
7 purchase totals =	$926.20		$1,012.8281	$1,012.84	$1,012.75	$1,012.80