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	$214.29	9.585%	$234.8297	$234.83	$234.85	$234.80
Purchase #2	$83.46	7.815%	$89.9824	$89.98	$90.00	$90.00
Purchase #3	$185.98	3.404%	$192.3108	$192.31	$192.30	$192.30
Purchase #4	$183.89	6.816%	$196.4239	$196.42	$196.40	$196.40
Purchase #5	$222.51	6.321%	$236.5749	$236.57	$236.55	$236.60
Purchase #6	$204.79	3.645%	$212.2546	$212.25	$212.25	$212.30
Purchase #7	$52.61	9.567%	$57.6432	$57.64	$57.65	$57.60
7 purchase totals =	$1,147.53		$1,220.0195	$1,220.00	$1,220.00	$1,220.00