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	$128.67	9.800%	$141.2797	$141.28	$141.30	$141.30
Purchase #2	$93.46	11.237%	$103.9621	$103.96	$103.95	$104.00
Purchase #3	$211.72	8.426%	$229.5595	$229.56	$229.55	$229.60
Purchase #4	$182.65	7.687%	$196.6903	$196.69	$196.70	$196.70
Purchase #5	$145.72	6.141%	$154.6687	$154.67	$154.65	$154.70
Purchase #6	$102.42	8.189%	$110.8072	$110.81	$110.80	$110.80
Purchase #7	$101.69	12.809%	$114.7155	$114.72	$114.70	$114.70
7 purchase totals =	$966.33		$1,051.6830	$1,051.69	$1,051.65	$1,051.80