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	$229.93	10.608%	$254.321	$254.32	$254.30	$254.30
Purchase #2	$52.73	5.693%	$55.7319	$55.73	$55.75	$55.70
Purchase #3	$43.90	5.846%	$46.4664	$46.47	$46.45	$46.50
Purchase #4	$120.76	7.271%	$129.5405	$129.54	$129.55	$129.50
Purchase #5	$70.66	10.687%	$78.2114	$78.21	$78.20	$78.20
Purchase #6	$79.27	4.507%	$82.8427	$82.84	$82.85	$82.80
Purchase #7	$72.39	12.148%	$81.1839	$81.18	$81.20	$81.20
7 purchase totals =	$669.64		$728.2978	$728.29	$728.30	$728.20