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	$94.71	7.375%	$101.6949	$101.69	$101.70	$101.70
Purchase #2	$213.60	3.744%	$221.5972	$221.60	$221.60	$221.60
Purchase #3	$249.32	4.789%	$261.2599	$261.26	$261.25	$261.30
Purchase #4	$123.27	3.494%	$127.5771	$127.58	$127.60	$127.60
Purchase #5	$150.73	7.569%	$162.1388	$162.14	$162.15	$162.10
Purchase #6	$129.57	9.847%	$142.3288	$142.33	$142.35	$142.30
Purchase #7	$32.54	3.661%	$33.7313	$33.73	$33.75	$33.70
7 purchase totals =	$993.74		$1,050.3280	$1,050.33	$1,050.40	$1,050.30