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	$155.42	3.448%	$160.7789	$160.78	$160.80	$160.80
Purchase #2	$47.91	12.336%	$53.8202	$53.82	$53.80	$53.80
Purchase #3	$66.25	9.869%	$72.7882	$72.79	$72.80	$72.80
Purchase #4	$67.27	8.280%	$72.84	$72.84	$72.85	$72.80
Purchase #5	$245.50	12.242%	$275.5541	$275.55	$275.55	$275.60
Purchase #6	$202.62	5.323%	$213.4055	$213.41	$213.40	$213.40
Purchase #7	$165.79	8.231%	$179.4362	$179.44	$179.45	$179.40
7 purchase totals =	$950.76		$1,028.6231	$1,028.63	$1,028.65	$1,028.60