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	$168.83	3.144%	$174.138	$174.14	$174.15	$174.10
Purchase #2	$177.65	4.354%	$185.3849	$185.38	$185.40	$185.40
Purchase #3	$54.33	13.430%	$61.6265	$61.63	$61.65	$61.60
Purchase #4	$112.30	13.441%	$127.3942	$127.39	$127.40	$127.40
Purchase #5	$38.28	6.619%	$40.8138	$40.81	$40.80	$40.80
Purchase #6	$114.75	7.791%	$123.6902	$123.69	$123.70	$123.70
Purchase #7	$177.53	13.669%	$201.7966	$201.80	$201.80	$201.80
7 purchase totals =	$843.67		$914.8442	$914.84	$914.90	$914.80