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	$228.77	11.543%	$255.1769	$255.18	$255.20	$255.20
Purchase #2	$55.85	6.730%	$59.6087	$59.61	$59.60	$59.60
Purchase #3	$163.39	9.620%	$179.1081	$179.11	$179.10	$179.10
Purchase #4	$233.67	7.152%	$250.3821	$250.38	$250.40	$250.40
Purchase #5	$35.29	10.237%	$38.9026	$38.90	$38.90	$38.90
Purchase #6	$114.56	9.845%	$125.8384	$125.84	$125.85	$125.80
Purchase #7	$248.85	7.424%	$267.3246	$267.32	$267.30	$267.30
7 purchase totals =	$1,080.38		$1,176.3414	$1,176.34	$1,176.35	$1,176.30