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	$133.55	6.809%	$142.6434	$142.64	$142.65	$142.60
Purchase #2	$242.54	12.801%	$273.5875	$273.59	$273.60	$273.60
Purchase #3	$178.48	4.389%	$186.3135	$186.31	$186.30	$186.30
Purchase #4	$24.47	8.865%	$26.6393	$26.64	$26.65	$26.60
Purchase #5	$80.40	12.361%	$90.3382	$90.34	$90.35	$90.30
Purchase #6	$147.64	5.734%	$156.1057	$156.11	$156.10	$156.10
Purchase #7	$249.88	6.465%	$266.0347	$266.03	$266.05	$266.00
7 purchase totals =	$1,056.96		$1,141.6623	$1,141.66	$1,141.70	$1,141.50