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	$30.54	4.115%	$31.7967	$31.80	$31.80	$31.80
Purchase #2	$186.85	6.146%	$198.3338	$198.33	$198.35	$198.30
Purchase #3	$221.69	7.619%	$238.5806	$238.58	$238.60	$238.60
Purchase #4	$123.84	3.812%	$128.5608	$128.56	$128.55	$128.60
Purchase #5	$96.27	8.619%	$104.5675	$104.57	$104.55	$104.60
Purchase #6	$99.44	4.264%	$103.6801	$103.68	$103.70	$103.70
Purchase #7	$195.32	7.157%	$209.2991	$209.30	$209.30	$209.30
7 purchase totals =	$953.95		$1,014.8186	$1,014.82	$1,014.85	$1,014.90