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	$195.88	10.442%	$216.3338	$216.33	$216.35	$216.30
Purchase #2	$225.36	8.747%	$245.0722	$245.07	$245.05	$245.10
Purchase #3	$197.61	6.484%	$210.423	$210.42	$210.40	$210.40
Purchase #4	$103.81	5.543%	$109.5642	$109.56	$109.55	$109.60
Purchase #5	$31.30	6.782%	$33.4228	$33.42	$33.40	$33.40
Purchase #6	$200.72	8.712%	$218.2067	$218.21	$218.20	$218.20
Purchase #7	$96.79	13.175%	$109.5421	$109.54	$109.55	$109.50
7 purchase totals =	$1,051.47		$1,142.5648	$1,142.55	$1,142.50	$1,142.50