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	$229.53	9.419%	$251.1494	$251.15	$251.15	$251.10
Purchase #2	$40.56	4.653%	$42.4473	$42.45	$42.45	$42.40
Purchase #3	$177.36	9.395%	$194.023	$194.02	$194.00	$194.00
Purchase #4	$68.61	7.801%	$73.9623	$73.96	$73.95	$74.00
Purchase #5	$72.65	13.474%	$82.4389	$82.44	$82.45	$82.40
Purchase #6	$174.57	7.804%	$188.1934	$188.19	$188.20	$188.20
Purchase #7	$196.99	12.845%	$222.2934	$222.29	$222.30	$222.30
7 purchase totals =	$960.27		$1,054.5077	$1,054.50	$1,054.50	$1,054.40