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	$210.56	8.366%	$228.1754	$228.18	$228.20	$228.20
Purchase #2	$163.59	13.655%	$185.9282	$185.93	$185.95	$185.90
Purchase #3	$101.87	3.751%	$105.6911	$105.69	$105.70	$105.70
Purchase #4	$188.43	13.512%	$213.8907	$213.89	$213.90	$213.90
Purchase #5	$45.34	3.399%	$46.8811	$46.88	$46.90	$46.90
Purchase #6	$31.51	12.616%	$35.4853	$35.49	$35.50	$35.50
Purchase #7	$189.42	12.839%	$213.7396	$213.74	$213.75	$213.70
7 purchase totals =	$930.72		$1,029.7914	$1,029.80	$1,029.90	$1,029.80