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	$85.58	7.254%	$91.788	$91.79	$91.80	$91.80
Purchase #2	$99.56	9.675%	$109.1924	$109.19	$109.20	$109.20
Purchase #3	$81.44	13.277%	$92.2528	$92.25	$92.25	$92.30
Purchase #4	$238.49	13.584%	$270.8865	$270.89	$270.90	$270.90
Purchase #5	$101.97	3.260%	$105.2942	$105.29	$105.30	$105.30
Purchase #6	$235.58	11.454%	$262.5633	$262.56	$262.55	$262.60
Purchase #7	$73.82	8.710%	$80.2497	$80.25	$80.25	$80.20
7 purchase totals =	$916.44		$1,012.2269	$1,012.22	$1,012.25	$1,012.30