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	$141.54	12.596%	$159.3684	$159.37	$159.35	$159.40
Purchase #2	$67.25	9.383%	$73.5601	$73.56	$73.55	$73.60
Purchase #3	$66.65	6.270%	$70.829	$70.83	$70.85	$70.80
Purchase #4	$130.28	9.300%	$142.396	$142.40	$142.40	$142.40
Purchase #5	$242.83	5.360%	$255.8457	$255.85	$255.85	$255.80
Purchase #6	$159.97	7.404%	$171.8142	$171.81	$171.80	$171.80
Purchase #7	$184.27	8.791%	$200.4692	$200.47	$200.45	$200.50
7 purchase totals =	$992.79		$1,074.2826	$1,074.29	$1,074.25	$1,074.30