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	$96.91	13.136%	$109.6401	$109.64	$109.65	$109.60
Purchase #2	$40.36	4.356%	$42.1181	$42.12	$42.10	$42.10
Purchase #3	$159.47	9.309%	$174.3151	$174.32	$174.30	$174.30
Purchase #4	$212.75	11.466%	$237.1439	$237.14	$237.15	$237.10
Purchase #5	$219.33	5.817%	$232.0884	$232.09	$232.10	$232.10
Purchase #6	$195.60	9.123%	$213.4446	$213.44	$213.45	$213.40
Purchase #7	$113.40	4.620%	$118.6391	$118.64	$118.65	$118.60
7 purchase totals =	$1,037.82		$1,127.3893	$1,127.39	$1,127.40	$1,127.20