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	$67.91	6.383%	$72.2447	$72.24	$72.25	$72.20
Purchase #2	$93.34	5.392%	$98.3729	$98.37	$98.35	$98.40
Purchase #3	$226.80	8.300%	$245.6244	$245.62	$245.60	$245.60
Purchase #4	$86.37	3.180%	$89.1166	$89.12	$89.10	$89.10
Purchase #5	$243.80	10.856%	$270.2669	$270.27	$270.25	$270.30
Purchase #6	$242.74	11.496%	$270.6454	$270.65	$270.65	$270.60
Purchase #7	$62.45	13.254%	$70.7271	$70.73	$70.75	$70.70
7 purchase totals =	$1,023.41		$1,116.9980	$1,117.00	$1,116.95	$1,116.90