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	$185.75	12.576%	$209.1099	$209.11	$209.10	$209.10
Purchase #2	$123.97	7.390%	$133.1314	$133.13	$133.15	$133.10
Purchase #3	$73.88	6.779%	$78.8883	$78.89	$78.90	$78.90
Purchase #4	$150.46	9.460%	$164.6935	$164.69	$164.70	$164.70
Purchase #5	$216.84	4.289%	$226.1403	$226.14	$226.15	$226.10
Purchase #6	$127.49	4.623%	$133.3839	$133.38	$133.40	$133.40
Purchase #7	$101.78	7.506%	$109.4196	$109.42	$109.40	$109.40
7 purchase totals =	$980.17		$1,054.7669	$1,054.76	$1,054.80	$1,054.70