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	$101.90	10.626%	$112.7279	$112.73	$112.75	$112.70
Purchase #2	$214.86	6.198%	$228.177	$228.18	$228.20	$228.20
Purchase #3	$222.32	9.473%	$243.3804	$243.38	$243.40	$243.40
Purchase #4	$191.47	3.596%	$198.3553	$198.36	$198.35	$198.40
Purchase #5	$174.88	12.395%	$196.5564	$196.56	$196.55	$196.60
Purchase #6	$50.72	8.633%	$55.0987	$55.10	$55.10	$55.10
Purchase #7	$195.93	10.466%	$216.436	$216.44	$216.45	$216.40
7 purchase totals =	$1,152.08		$1,250.7317	$1,250.75	$1,250.80	$1,250.80