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	$194.53	5.519%	$205.2661	$205.27	$205.25	$205.30
Purchase #2	$107.63	7.302%	$115.4891	$115.49	$115.50	$115.50
Purchase #3	$96.82	8.563%	$105.1107	$105.11	$105.10	$105.10
Purchase #4	$153.41	12.609%	$172.7535	$172.75	$172.75	$172.80
Purchase #5	$80.62	10.672%	$89.2238	$89.22	$89.20	$89.20
Purchase #6	$153.72	9.524%	$168.3603	$168.36	$168.35	$168.40
Purchase #7	$227.56	4.114%	$236.9218	$236.92	$236.90	$236.90
7 purchase totals =	$1,014.29		$1,093.1253	$1,093.12	$1,093.05	$1,093.20