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	$163.78	10.405%	$180.8213	$180.82	$180.80	$180.80
Purchase #2	$136.90	7.779%	$147.5495	$147.55	$147.55	$147.50
Purchase #3	$144.73	10.581%	$160.0439	$160.04	$160.05	$160.00
Purchase #4	$151.86	7.111%	$162.6588	$162.66	$162.65	$162.70
Purchase #5	$45.27	6.336%	$48.1383	$48.14	$48.15	$48.10
Purchase #6	$194.33	3.191%	$200.5311	$200.53	$200.55	$200.50
Purchase #7	$96.89	8.623%	$105.2448	$105.24	$105.25	$105.20
7 purchase totals =	$933.76		$1,004.9877	$1,004.98	$1,005.00	$1,004.80