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	$191.70	3.400%	$198.2178	$198.22	$198.20	$198.20
Purchase #2	$19.29	7.314%	$20.7009	$20.70	$20.70	$20.70
Purchase #3	$219.50	6.553%	$233.8838	$233.88	$233.90	$233.90
Purchase #4	$242.53	3.458%	$250.9167	$250.92	$250.90	$250.90
Purchase #5	$158.31	8.603%	$171.9294	$171.93	$171.95	$171.90
Purchase #6	$30.66	5.753%	$32.4239	$32.42	$32.40	$32.40
Purchase #7	$135.48	5.854%	$143.411	$143.41	$143.40	$143.40
7 purchase totals =	$997.47		$1,051.4835	$1,051.48	$1,051.45	$1,051.40