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	$89.43	7.368%	$96.0192	$96.02	$96.00	$96.00
Purchase #2	$196.88	4.259%	$205.2651	$205.27	$205.25	$205.30
Purchase #3	$143.83	9.306%	$157.2148	$157.21	$157.20	$157.20
Purchase #4	$95.58	4.451%	$99.8343	$99.83	$99.85	$99.80
Purchase #5	$175.64	7.654%	$189.0835	$189.08	$189.10	$189.10
Purchase #6	$168.79	3.418%	$174.5592	$174.56	$174.55	$174.60
Purchase #7	$231.98	13.509%	$263.3182	$263.32	$263.30	$263.30
7 purchase totals =	$1,102.13		$1,185.2943	$1,185.29	$1,185.25	$1,185.30