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	$134.49	5.126%	$141.384	$141.38	$141.40	$141.40
Purchase #2	$135.27	12.739%	$152.502	$152.50	$152.50	$152.50
Purchase #3	$52.69	7.265%	$56.5179	$56.52	$56.50	$56.50
Purchase #4	$229.60	6.791%	$245.1921	$245.19	$245.20	$245.20
Purchase #5	$233.29	11.331%	$259.7241	$259.72	$259.70	$259.70
Purchase #6	$86.25	11.383%	$96.0678	$96.07	$96.05	$96.10
Purchase #7	$162.91	11.814%	$182.1562	$182.16	$182.15	$182.20
7 purchase totals =	$1,034.50		$1,133.5441	$1,133.54	$1,133.50	$1,133.60