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	$148.88	12.869%	$168.0394	$168.04	$168.05	$168.00
Purchase #2	$74.45	3.847%	$77.3141	$77.31	$77.30	$77.30
Purchase #3	$222.28	12.257%	$249.5249	$249.52	$249.50	$249.50
Purchase #4	$148.39	5.540%	$156.6108	$156.61	$156.60	$156.60
Purchase #5	$238.65	12.744%	$269.0636	$269.06	$269.05	$269.10
Purchase #6	$32.95	13.543%	$37.4124	$37.41	$37.40	$37.40
Purchase #7	$58.40	9.180%	$63.7611	$63.76	$63.75	$63.80
7 purchase totals =	$924.00		$1,021.7263	$1,021.71	$1,021.65	$1,021.70