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	$211.28	5.661%	$223.2406	$223.24	$223.25	$223.20
Purchase #2	$80.88	12.670%	$91.1275	$91.13	$91.15	$91.10
Purchase #3	$170.33	13.552%	$193.4131	$193.41	$193.40	$193.40
Purchase #4	$172.82	3.464%	$178.8065	$178.81	$178.80	$178.80
Purchase #5	$130.76	4.183%	$136.2297	$136.23	$136.25	$136.20
Purchase #6	$78.28	9.141%	$85.4356	$85.44	$85.45	$85.40
Purchase #7	$104.85	7.214%	$112.4139	$112.41	$112.40	$112.40
7 purchase totals =	$949.20		$1,020.6669	$1,020.67	$1,020.70	$1,020.50