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	$223.81	6.506%	$238.3711	$238.37	$238.35	$238.40
Purchase #2	$249.76	13.245%	$282.8407	$282.84	$282.85	$282.80
Purchase #3	$92.79	13.515%	$105.3306	$105.33	$105.35	$105.30
Purchase #4	$131.76	6.744%	$140.6459	$140.65	$140.65	$140.60
Purchase #5	$95.37	4.225%	$99.3994	$99.40	$99.40	$99.40
Purchase #6	$163.86	10.144%	$180.482	$180.48	$180.50	$180.50
Purchase #7	$57.56	11.713%	$64.302	$64.30	$64.30	$64.30
7 purchase totals =	$1,014.91		$1,111.3717	$1,111.37	$1,111.40	$1,111.30