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	$95.27	6.367%	$101.3358	$101.34	$101.35	$101.30
Purchase #2	$43.89	9.436%	$48.0315	$48.03	$48.05	$48.00
Purchase #3	$173.57	8.304%	$187.9833	$187.98	$188.00	$188.00
Purchase #4	$243.40	12.864%	$274.711	$274.71	$274.70	$274.70
Purchase #5	$187.27	12.441%	$210.5683	$210.57	$210.55	$210.60
Purchase #6	$85.29	4.489%	$89.1187	$89.12	$89.10	$89.10
Purchase #7	$86.48	7.406%	$92.8847	$92.88	$92.90	$92.90
7 purchase totals =	$915.17		$1,004.6333	$1,004.63	$1,004.65	$1,004.60