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	$194.69	11.156%	$216.4096	$216.41	$216.40	$216.40
Purchase #2	$28.86	12.445%	$32.4516	$32.45	$32.45	$32.50
Purchase #3	$162.63	13.374%	$184.3801	$184.38	$184.40	$184.40
Purchase #4	$186.41	12.470%	$209.6553	$209.66	$209.65	$209.70
Purchase #5	$96.52	13.663%	$109.7075	$109.71	$109.70	$109.70
Purchase #6	$75.99	9.118%	$82.9188	$82.92	$82.90	$82.90
Purchase #7	$78.59	4.603%	$82.2075	$82.21	$82.20	$82.20
7 purchase totals =	$823.69		$917.7304	$917.74	$917.70	$917.80