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	$169.39	7.757%	$182.5296	$182.53	$182.55	$182.50
Purchase #2	$136.56	4.634%	$142.8882	$142.89	$142.90	$142.90
Purchase #3	$201.59	5.128%	$211.9275	$211.93	$211.95	$211.90
Purchase #4	$233.74	5.156%	$245.7916	$245.79	$245.80	$245.80
Purchase #5	$80.85	10.287%	$89.167	$89.17	$89.15	$89.20
Purchase #6	$186.31	4.345%	$194.4052	$194.41	$194.40	$194.40
Purchase #7	$127.75	5.498%	$134.7737	$134.77	$134.75	$134.80
7 purchase totals =	$1,136.19		$1,201.4828	$1,201.49	$1,201.50	$1,201.50