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	$90.83	6.736%	$96.9483	$96.95	$96.95	$96.90
Purchase #2	$218.53	4.405%	$228.1562	$228.16	$228.15	$228.20
Purchase #3	$79.64	6.566%	$84.8692	$84.87	$84.85	$84.90
Purchase #4	$198.40	11.737%	$221.6862	$221.69	$221.70	$221.70
Purchase #5	$197.67	10.429%	$218.285	$218.29	$218.30	$218.30
Purchase #6	$127.50	11.280%	$141.882	$141.88	$141.90	$141.90
Purchase #7	$65.86	8.694%	$71.5859	$71.59	$71.60	$71.60
7 purchase totals =	$978.43		$1,063.4128	$1,063.43	$1,063.45	$1,063.50