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	$229.71	4.414%	$239.8494	$239.85	$239.85	$239.80
Purchase #2	$90.33	5.154%	$94.9856	$94.99	$95.00	$95.00
Purchase #3	$99.79	11.651%	$111.4165	$111.42	$111.40	$111.40
Purchase #4	$59.44	4.753%	$62.2652	$62.27	$62.25	$62.30
Purchase #5	$204.75	8.642%	$222.4445	$222.44	$222.45	$222.40
Purchase #6	$240.45	3.618%	$249.1495	$249.15	$249.15	$249.10
Purchase #7	$35.84	12.797%	$40.4264	$40.43	$40.45	$40.40
7 purchase totals =	$960.31		$1,020.5371	$1,020.55	$1,020.55	$1,020.40