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	$185.74	3.270%	$191.8137	$191.81	$191.80	$191.80
Purchase #2	$54.60	7.376%	$58.6273	$58.63	$58.65	$58.60
Purchase #3	$248.28	8.512%	$269.4136	$269.41	$269.40	$269.40
Purchase #4	$82.76	7.617%	$89.0638	$89.06	$89.05	$89.10
Purchase #5	$183.26	3.803%	$190.2294	$190.23	$190.25	$190.20
Purchase #6	$139.57	12.115%	$156.4789	$156.48	$156.50	$156.50
Purchase #7	$44.46	5.738%	$47.0111	$47.01	$47.00	$47.00
7 purchase totals =	$938.67		$1,002.6378	$1,002.63	$1,002.65	$1,002.60