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	$175.82	3.119%	$181.3038	$181.30	$181.30	$181.30
Purchase #2	$189.98	4.422%	$198.3809	$198.38	$198.40	$198.40
Purchase #3	$100.62	10.238%	$110.9215	$110.92	$110.90	$110.90
Purchase #4	$220.67	5.866%	$233.6145	$233.61	$233.60	$233.60
Purchase #5	$120.33	9.124%	$131.3089	$131.31	$131.30	$131.30
Purchase #6	$191.70	9.270%	$209.4706	$209.47	$209.45	$209.50
Purchase #7	$88.91	12.606%	$100.118	$100.12	$100.10	$100.10
7 purchase totals =	$1,088.03		$1,165.1182	$1,165.11	$1,165.05	$1,165.10