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	$119.59	3.234%	$123.4575	$123.46	$123.45	$123.50
Purchase #2	$156.45	8.548%	$169.8233	$169.82	$169.80	$169.80
Purchase #3	$185.80	5.642%	$196.2828	$196.28	$196.30	$196.30
Purchase #4	$197.28	7.518%	$212.1115	$212.11	$212.10	$212.10
Purchase #5	$44.69	5.705%	$47.2396	$47.24	$47.25	$47.20
Purchase #6	$209.50	6.298%	$222.6943	$222.69	$222.70	$222.70
Purchase #7	$149.28	11.572%	$166.5547	$166.55	$166.55	$166.60
7 purchase totals =	$1,062.59		$1,138.1637	$1,138.15	$1,138.15	$1,138.20