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	$209.33	5.513%	$220.8704	$220.87	$220.85	$220.90
Purchase #2	$28.55	12.542%	$32.1307	$32.13	$32.15	$32.10
Purchase #3	$71.72	9.626%	$78.6238	$78.62	$78.60	$78.60
Purchase #4	$174.80	4.264%	$182.2535	$182.25	$182.25	$182.30
Purchase #5	$239.83	4.563%	$250.7734	$250.77	$250.75	$250.80
Purchase #6	$72.49	12.595%	$81.6201	$81.62	$81.60	$81.60
Purchase #7	$188.81	8.736%	$205.3044	$205.30	$205.30	$205.30
7 purchase totals =	$985.53		$1,051.5763	$1,051.56	$1,051.50	$1,051.60