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	$162.79	5.692%	$172.056	$172.06	$172.05	$172.10
Purchase #2	$220.64	5.727%	$233.2761	$233.28	$233.30	$233.30
Purchase #3	$198.57	10.117%	$218.6593	$218.66	$218.65	$218.70
Purchase #4	$110.73	10.628%	$122.4984	$122.50	$122.50	$122.50
Purchase #5	$80.94	6.302%	$86.0408	$86.04	$86.05	$86.00
Purchase #6	$176.82	10.874%	$196.0474	$196.05	$196.05	$196.00
Purchase #7	$35.33	7.440%	$37.9586	$37.96	$37.95	$38.00
7 purchase totals =	$985.82		$1,066.5366	$1,066.55	$1,066.55	$1,066.60