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	$151.81	5.814%	$160.6362	$160.64	$160.65	$160.60
Purchase #2	$5.71	5.612%	$6.0304	$6.03	$6.05	$6.00
Purchase #3	$135.82	5.370%	$143.1135	$143.11	$143.10	$143.10
Purchase #4	$229.32	11.554%	$255.8156	$255.82	$255.80	$255.80
Purchase #5	$198.36	12.493%	$223.1411	$223.14	$223.15	$223.10
Purchase #6	$136.80	12.776%	$154.2776	$154.28	$154.30	$154.30
Purchase #7	$111.64	10.229%	$123.0597	$123.06	$123.05	$123.10
7 purchase totals =	$969.46		$1,066.0741	$1,066.08	$1,066.10	$1,066.00