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	$197.66	5.790%	$209.1045	$209.10	$209.10	$209.10
Purchase #2	$30.30	5.400%	$31.9362	$31.94	$31.95	$31.90
Purchase #3	$178.47	3.402%	$184.5415	$184.54	$184.55	$184.50
Purchase #4	$238.90	4.376%	$249.3543	$249.35	$249.35	$249.40
Purchase #5	$195.69	7.493%	$210.3531	$210.35	$210.35	$210.40
Purchase #6	$71.66	12.419%	$80.5595	$80.56	$80.55	$80.60
Purchase #7	$245.33	4.507%	$256.387	$256.39	$256.40	$256.40
7 purchase totals =	$1,158.01		$1,222.2361	$1,222.23	$1,222.25	$1,222.30