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	$245.28	10.432%	$270.8676	$270.87	$270.85	$270.90
Purchase #2	$176.55	11.523%	$196.8939	$196.89	$196.90	$196.90
Purchase #3	$87.49	11.324%	$97.3974	$97.40	$97.40	$97.40
Purchase #4	$184.85	13.221%	$209.289	$209.29	$209.30	$209.30
Purchase #5	$57.92	3.135%	$59.7358	$59.74	$59.75	$59.70
Purchase #6	$96.73	5.322%	$101.878	$101.88	$101.90	$101.90
Purchase #7	$156.46	10.215%	$172.4424	$172.44	$172.45	$172.40
7 purchase totals =	$1,005.28		$1,108.5041	$1,108.51	$1,108.55	$1,108.50