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	$108.80	7.515%	$116.9763	$116.98	$117.00	$117.00
Purchase #2	$127.44	12.764%	$143.7064	$143.71	$143.70	$143.70
Purchase #3	$95.72	4.798%	$100.3126	$100.31	$100.30	$100.30
Purchase #4	$90.90	3.498%	$94.0797	$94.08	$94.10	$94.10
Purchase #5	$48.34	12.492%	$54.3786	$54.38	$54.40	$54.40
Purchase #6	$131.41	6.419%	$139.8452	$139.85	$139.85	$139.80
Purchase #7	$181.73	13.219%	$205.7529	$205.75	$205.75	$205.80
7 purchase totals =	$784.34		$855.0517	$855.06	$855.10	$855.10