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	$157.73	9.305%	$172.4068	$172.41	$172.40	$172.40
Purchase #2	$67.88	6.859%	$72.5359	$72.54	$72.55	$72.50
Purchase #3	$114.79	8.264%	$124.2762	$124.28	$124.30	$124.30
Purchase #4	$211.60	4.661%	$221.4627	$221.46	$221.45	$221.50
Purchase #5	$163.38	11.129%	$181.5626	$181.56	$181.55	$181.60
Purchase #6	$51.55	4.661%	$53.9527	$53.95	$53.95	$54.00
Purchase #7	$107.30	7.283%	$115.1147	$115.11	$115.10	$115.10
7 purchase totals =	$874.23		$941.3116	$941.31	$941.30	$941.40